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immediate connexion with [that of] the second, the describersof form conjectured what the structure ought to be by con-sulting the works of the anatomist ; and the anatomist con-jectured what the living history is or ought to be from thenatural history of others, filling up what he conceived to bejust and fancy supplying the rest. But such union of know-

ledge does not properly match. It is one building built at Idifferent times-an addition to an original plan. It is nowonder, therefore, that the whole is imperfect." Can we

pronounce all later anatomists and writers on natural historyto be free from this reproach? John Hunter’s remarkablememoir on the Life-history of Bees testifies to his excellenceas a naturalist. For the convenience of close continuousobservation of his bees without molesting them he had hivesmade with glass windows, which allowed him at all timesto watch their occupants. He inquires into the causes ofthe deaths of certain bees in winter ; he mentions that"there was plenty of honey in their hive ; that on closelyexamining the dead bees he found they all died with theirproboscides extended, their stomachs were full of honey, andtheir intestines, especially the last part, also full of excre-ment." No circumstance, however minute, eluded his notice.He comments on the heat of bees, and remarks that withoutwarmth they become dull, inactive, and torpid. He tells uathat "on July 18th, at ten in the evening, wind northerly,thermometer at 54° in the open air, I introduced it into thetop of a hive full of bees, and in less than five minutes it roseto 82°. I let it stand all night. At five in the morning itwas down to 79°, at nine in the same morning it had risen to83°, and at one o’clock to 84°, and at nine in the eveningit was down to 780. Dec. 30th. Air at 35°, bees at

73°." John Hunter made the diecovery that the wax isnot gathered by the bees from flowers, as is "farina"(pollen), but it "is formed by the bees themselves." Hesays: "It may be called an external secretion of oil.......It is formed between each scale on the under surface ofthe belly." He detaches the minute fiake, warms it on thepoint of a needle in the flame of a candle, sees it melt andrun into a bead, and then burn in the manner of wax-inshort, it is wax. Then he describes the building of the comband of the royal cell ; the deposition of eggs by the queen,their attachment to the bottom of the cells, and theiroccasional transference from the cells in which they werefirst placed to other cells ; the storing of bee-bread for

feeding the grubs; the development of the grab, its pupalphase, and final escape from the cell as the imago. Henotes the different life forms present in the community-thequeen, the males, and "the working bee, which cannot becalled either sex." Lastly, he describes the anatomy ofthe bee and comments on its special senses. With equalthoroughness he investigated the life-history and habitsof the wasps and the hornets. We also find him occu-

pied in a study of the economy and anatomy of thehumble-bee (Bombus terrestris), on which subject he has lefta long note. With untiring industry he examined all theoccupants of one nest, and found them to comprise 157females and twenty-five males, and he noted that the formerhad longer proboscides than the latter. The humble-beedoes not, he tells us, colonise, like the honey bee ; it doesnot swarm like these, but the family is begun by a singlefemale, assisted later by her offspring. None but youngqueens live through the winter, on the approa,ch of whichthey leave their nests and seek winter quarters in holes indry banks and similar places, from which they emerge in thefollowing spring. About May the humble bees construct theirhives, which are usually beneath ground. He describes in con-siderable detail their structure, the deposition of the egg by thequeen, the grubs which result from these, and their life-

history, ending in the image stage. The black humble-bee(Anthophora retusa) and the "leaf-celled bee" (Megachilecentuncularis) were also objects of his study. He noticesthe habit of the latter of cutting pieces of the leaves of roses,strawberries, and flgwood, and he admires the dexterity theyevince in carrying these into their holes, and the skill andneatness shown in adapting them to the construction of theircells. His attention was not limited to Hymenoptera, for wefind him busy with beetles. Of the dung-beetle (Geotrupesstejcoranns) he records that in June he found the grubsnearly ready to assume the pupal phase, and that the perfectbeetle emerged at the end of Jaly or in August. The nestsenclosing the grubs are holes from twelve to eighteen inchesbelow the surface of the ground, usually near cow dung.These and also other holes pierced for the purpose they usefor winter quarters. Most of them die, but a few survive till

the following spring. Of the common cockchafer (Melolontbavulgaris) and the rose-beetle (Cetonia aurata) he hasalso left short notes. In Orthoptera he describes atsome length the grasshopper (Phasgonenron viridissimum),with special notice of the external appearance and theanatomy of its eye. He detects the predatory habit of thedragon. fly (aesthna grandis), concerning which he makesthe following thoroughly characteristic note: "Aug. 18th,1778, at eight o’clock in the evening, I saw the dragon-flyflying about, making short turns, which were performed veryquick. I also observed gnats fi,iDg; and what took myattention most was his making up to a gnat, and the gnatwas seen no more ; therefore I conjectured he was feedingupon them. I caught him and opened him next morning.and could observe in the stomach the scales of some insects."What a picture this little anecdote gives of the acuteness ofJohn Hunter as a field naturalist.As a zootomist and morphologist John Hunter could not

be satisfied with the highly artificial zoological classificationscurrent in his day. He remarks on the want of an adequateknowledge of these preliminary and indispensable studies,which led even the great classifier Linnseaa into some verysingular arrangements in the earlier editions of his II SystemaNaturae," of which he notices one-viz., the placing together,in one order of mammalia, man, the elephant, and the bat,because in each the mammœ are pectorally situated. Suchclassifying as this, he caustically observes, may be pertinent asregards nipples, but not as regards animals. He did not stopat showing the defects of the current artificial systems ofclassification of animals, but he suggested as bases for anatural classification the arrangements of the vascular, therespiratory, and the nervous systems; and he tentatively drewout the scheme of a natural classification founded on a com-bination of what he termed essential and circumstantialcharacters. Thus, of the class Mammalia he gives as essentialcharactets a four-chambered heart, lungs confined in a propercavity, the enlargement of which is the cause of respiration,lungs divided into small cells, respiration quick, viviparous,&c. ; whilst circumstantial characters are found in thestructure of the auditory organ. Thii illustration willsuffice to prove how sound and how advanced were JohnHunter’s views as a systematic zoologist.

If in this sketch of John Hunter, imperfect, incomplete asI know it to be, I have succeeded in some small degree inpresenting him to you as one of the most indefatigableworkers, one of the most earnest seekers after truth, one ofthe very closest of skilled observers, one of the most sagaciousexpositors of vegetable and animal life, I shall not have also-gether failed in accomplishing the design which I wished tooffer yon on this commemorative day- presentment of JohnHunter as a biologist in the widest sense of this now mucb-used word. For this I have made large use of his ownwords, because these best show his mind, and "the mind isthe man."

The Arris and Gale LecturesON

THE CENTRAL NERVOUS MECHANISM OFTHE RESPIRATION.

Delivered before the Royal College of Surgeons on Feb. 18thand 20th, 1895,

BY WALTER SPENCER, M.S., M.B. LOND.,F.R.C.S.ENG.,

SURGLON TO OUT-PATIENTS AND TO THE THROAT DEPARTMENT, WEST-MINSTER HOSPITAL ; LECTURER ON PHYSIOLOGY IN THE

MEDICAL SCHOOL.

LECTURE I.

GENTLEMEN,-In these three lectures I propose to givean account of the nervous mechanism which producesrespiration and to point out some of the practical usesto which this knowledge may be put. In doing so

I have no wish unduly to separate this particular physio-logical action from the other vital functions of the nervematter situated in the base of the brain. It is closelyallied with the vascular mechanism and with the internalor tissue respiration producing heat. I began to makeobservations on this subject when I was collecting matter

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for the essay on Intracranial Tumours and Abscess which re-ceived the Jacksonian prize. The work has been carried outat first at the laboratory of the Brown Institution and later inthe pathological laboratory of University College. I amindebted to the Royal Society and also to the British MedicalAssociation for grants of money towards the expenses of thisresearch. My thanks are also due to Mr. Horsley for muchhelp in connexion with the work.

HISTORY, COMPARATIVE ANATOMY, AND PHYSIOLOGY.

LTEic; Iscturer then gave a résumé of the views heldabout the respiratory function from ancient times downto Legallois, in whose works, published in 1830, the

subject of the central nervous mechanism of the respi-lation was practically first treated. He then proceeded to con-sider the comparative anatomy and physiology of the respira-tory function, and showed from specimens in the museumof the College how the alimentary canal is used for reapira-tion. (a) throughout its own leogth (a laach), (b) in itsanterior part (salamander and amphioxus), and Co) bydivertioula (gtlis or lungs). In certain fishes the air bladderis used as a storehouse for oxygen. In the higher animalsmuscles are used for respiration which in lower formsare either used for progression or are connected with thealimentary canal. Mr. Spencer then went on to speakof:]The connexion of the automatic movement of respiration

with the roots ff the vagi, nerves in the bulb.-In thepharyngeal form of respiration these nerves are both theafferent and efferent channel for the gill arches. In mam-mals it remains the chief afferent channel to the respira-tory centre, but its efferent connexions are limited to thela.ryux, the facial nerve above baing the channel forthe nose, and asi the muscles of the thorax take on

a respiratory action efferent impulses go by the spinalcord.

Tf1,e sazpreJrzactl of the bulb over respiration and the sub-ordinate influence of the spinal cord. - Legallois 1 was the firstto show that an animal continued to breathe regularly afterthe removal of the cerebrum, cerebellum, and part of thebulb, so long as the section was made above the roots of thevagus group of nerves. On an injury to the origin of thesenerves respiration finally ceased. The respiratory functionwas thus taken out of the category of voluntary movements,in which it had been previously included. Although respira-tion continues regularly for some time after section of thebolb immediately above the vagus roots, yet within a fewhours the animal dies, for the highest centre for heat pro-duction and internal respiration and the vaso-motor centreare cut off, and thus a warm-blooded animal cannotlive for any length of time. A section through or

below the roots of the vagi destroys all respiratorymovement except that of the nose and jaw. So longas the roots of the facial are intact rhythmic move-ments of the nose and jaw occur during asphyxia-that is, ,when the facial nuclei have been quite separated from thevagi. The transverse section of the bulb immediately belowthe tubercula acustica abolishes all reflex sensory effects

upon respiration from the cornea or nose, as well as therhytbmic movements of the nostrils-the facial muscles beingeither abuve the section or actually traversed by it. The firsttransverse section immediately affecting respiration runs justbelow the facial nucleus. The respiration becomes deeperand slow, with prolonged inspiration, just as after section ofboth vagi in the neck;3 in other words, the regulatory fibresof the lungs are connected with the highest part of the

centre, and this f act has been confirmed by finding that thefibres enter the bulb by what is now called the "glosso-pharyngeal root." A transverse section at the level of thealas cinereae causes the respiratory movements to becomeirregular, sometimes periodic, and breathing comes to astandstill altogether by passing through the stages ofasphyxia. Evidence as to a similar limit to the respiratorycentre in man has been obtained from anencephalousmonsters in which life has been prolonged even forfour days.A foetus in whom the cerebrum and part of the cerebellumhad been destroyed during birth continued to breathe regularly?it the rate of six per minute after complete section of’the

1 Legallois: Œuvres, tome i. Paris, 1830.2 Flourens: Du Système Nerveux, p. 199. 1842.

3 Markwald: The Movements of Respiration. London, 1888.4 Lallemand: Recherches Anatomiques sur l’Encéphale, tome iii.,

p. 230. Arnold: Bemerkungen über den Bau des Hirns und Rücken-marks. Zürich, 1838. Lawrence: Medico-Chirurgical Transactions,1814, vol. v., p. 165.

bulb by scissors 1 cm. above the calamus scriptorius.5 But asection immediately below the calamus abolished allrespira-tion together with the reflexes. The effect of dividing thespinal cord below the bulb was known to Galen.6 He statedthat when the spinal cord was divided between the first andsecond cervical vertebrm the animal immediately died, whenbetween the third and fourth natural respiration was lost, andwhen below the sixth the diaphragm continued in action, themuscles of the thorax remaining stationary. After a sectionlower down the thoracic muscles were capable of movement.The effect of such injuries to the spinal cord are, unfor.

tunately, too well known in man. Rhythmic movements ofthe facial muscles may continue for a long time if artificialrespiration be intermittently performed. When the bulb isisolated7 by dividing it from the cerebrum, cutting the vaginerves and the spinal cord below the sixth cervical vertebrae,the diaphragm continues in regular action. In a frog thecerebrum, including the mesencephalon, has been removedand the cord divided behind the atlas and destroyed, the lungsand even the heart extirpated, so that the bulb is entirely cutoff from all peripheral influences, only 5 mm. of brain matterbeing left. Yet regular movements of the mouth, nose, andvocal cords go on, and traces of respiratory movement havebeen found so long as twenty hours afterwards. Experimentssuch as the foregoing seem to show clearly the supremacyof the bulb over the respiratory movement, and the un-impaired connexion of the spinal nerve roots with the bulba sine quâ raon. Yet some have held the view that theganglion cells in the anterior cornua of the spinal cord are thereal sources of the movement, the bulb merely o(,,6rdinatingthe whole. This opinion is founded upon the occurrence ofrhythmic movements of the respiratory muscles after theseparation of the cord from the bulb. They are seen in new-born animals9 which are kept warm, in animals of about sixmonths when strychnine has been administered; 10 in adultdogs after artificial respiration has been kept up from one tofour hours." In all these cases there is a very high excita-bility of the spinal cord, so that rhythmic movements ofthe limbs occur along with those of the trunk, and allreflexes are exaggerated. The rhythmic movements ofthe respiratory muscles in no way aid respiration. Theanimal dies as quickly when they occur as when theydo not unless artificial respiration be performed. Indeed,there is no real inspiration lc from enlargement .of thethorax, for it is the muscles of extraordinary expirationwhich act strongly and without coordination, so thatalthough the thorax may be rhythmically constricted itnever dilates during such movements beyond the position ofrest. The only positive evidence in favour of inspirationoccurring after division of the spinal cord from the bulb isfurnished by Langendorff’s 13 experiments upon the tortoise.After the division the inspirations as seen in his tracingsbecome very much less and are followed by a forced expira-tion. If the small inspiration recorded be not due to someerror in the experiment, such as the recoil of the lever beyondthe position of rest after the forced expiration, one mustadmit that a small inspiration can be produced by thespinal respiratory centres of the tortoise. The arrest of

respiration on section of the cord just below the bulb hasbeen attributed to inhibition from the effect of the injary(shock).14 A much longer incision, however, can be madeexactly in the middle line of the same region of the cordwithout affecting respiration, and a section above the rootsof the vagi, were the arrest caused by inhibition, ought tohave a like effect.

Brown-Séquard, however, in his last paper maintained theposition he had always held-viz., that respiration was de-pendent upon nerve elements to be found throughout the baseof the encephalon and cord. He laid special stress uponthose cases in man in which a tumour involved the bulb,and in those in which a dislocation of the axis uponthe atlas vertebra causes the odontoid process to press

5 Kehrer: Zeitschrift für Biologie, 1892, Band xxviii., p. 450.6 Galen: De Anatomicis Administrationibus. Kühn, lib. viii., cap.ix.

De Symptomatum Causis, lib. i., cap. v.7 Rosenthal : Archiv fur (Anatomie und) Physiologie, 1865, p. 191.

8 Langendorff : Ibid., 1887, p. 285.9 Brown-Séquard: Journal de Physiologie, 1860, tome iii., p. 151.

Archives de Physiologie, 1890, p. 371; 1893, p. 131.10 Rokitansky (Procop): Medicinische Jahrbücher, 1874, p. 30.

11 Wertheimer: Journal de l’Anatomie et de la Physiologie, 1886,tome xxii., p. 458.

12 Markwald: Loc. cit. Laborde: Comptes-rendus de la Société deBiologie, 1890, tome ii., p. 620.13 Langendorff : Archiv für (Anatomie und) Physiologie, 1891, p. 486

14 Langendorff und Nitschmann: Ibid., 1880, p.510.

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backwards upon the cord. In such cases breathing con-tinued for some time, although in some of the cases

there was paralysis of the limbs and larynx. Thesecases of tumour in the bulb were many of them recordedlong ago, and only scanty details are given as to the part ofthe bulb actually involved. Paralysis of the limbs simplyproves the pyramids to have been affected, and the laryngealparalysis may have arisen from pressure on the vagus roots.There has been no microscopical evidence to show that theregion of the roots of the vagi were actually involved, andthe tendency of slow growing tumours to displace nerveelements without robbing them of their functions is wellknown. A gradual dislocation backwards of the odontoidprocess narrows the foramen magnum antero-posteriorlywithout necessarily pressing on the lateral columns in whichthe respiratory tracts descend. Moreover, cases of disloca-tion of the odontoid process ultimately die from impairedrespiration. If one were to assume that a specimen of adislocated axis had reached the full displacement found postmortem without impairing the breathing, we should be unableto explain the patient’s death and the impaired breathingwhich preceded it.

°

[Mr. Spencer then went on to consider the different con-nexions of the respiratory centre. In mentioning the dis-crepancies that obtain in the results of different observers,he pointed out how necessary it was that the degree of anses-thesia should be carefully recognised. He then continued :]The respiratory centre can be affected by the excitation

(a) of the vagi nerves, (b) of the cortex cerebri, (c) ofall sensory nerves, and (d) of the floor of the fourthventricle.

(a) The vagi nerves.-Owing to the differences in thedescription and nomenclature of the nerves passing throughthe jugular foramen considerable confusion has arisen. Thenerves called glosso-pharyngeal, vagus, and spinal accessoryoutside the skull do not correspond in the composition of theirfibres with the intracranial nerve roots which bear thesenames. Some have assumed that these nerves could bedivided into a sensory and motor portion like a spinal nerve,whereas all evidence tends to show that the fibres outside thebulb are completely mixed. It is a matter for regret that thedescription given by Willis 15 and illustrated in his drawinghas not been generally followed. He speaks of the eighthpair of nerves as the vagi or wandering pair, using the wordvagus in an anatomical sense. He likewise employs the termaccessorius in its primary anatomical meaning to describe hisspinal nerve as approaching and adhering to the vagns. The

chapter containing his discovery of the nerve is entitled " Ofthe Spinal Nerve, an Accessory to the Wandering Pair." Bymany writers a physiological significance has been imported,as if the word accessory were used in its secondary sense ofaiding the vagus. This error of using the term accessoryin its secondary sense of aiding has led to the furthererror of applying this term to fibres which do indeed aidthe vagus-viz., the lowest of the fibres arising from thebulb, which Willis included in the vagus. Thus the spinalaccessory of one writer has a spinal origin, and the spinalaccessory of another has a bulbar origin. I shall keepto the description of Willis and apply the word vagus toall the roots arising from the bulb. The spinal acces-

sory nerve of Willis is quite distinct from the vagus, bothin its origin, in its course, and in its distribution to thesterno-mastoid and trapezius, and finally, as I shall show, inits structure. It is absent in fish and snakes, whilst in otherreptiles, amphibia, and birds it varies according to the develop-ment of the neck muscles to which it is distributed. Thevagi, on the other hand. are constant in all vertebrates,arising from the lower half of the bulb in a well-developedform. By careful dissection the spinal nerve of Willis can beeasily separated from its adhesions to the lower roots of thevagus. In man, no doubt, the fibrous sheath is tough and thenerves have generally softened from post-mortem decomposi-tion. But in the stillborn foetus I have found no difficultyin separating the spinal accessory away from the vagus bysimply using needles. The same can be done in the species ofmonkey (Maccacus rhesus) I used in my experiments, in agibbon I dissected at the Zoological Gardens by the kindnessof Mr. Beddard, in a chimpanzee which had been experimentedupon by Messrs. Beevor and Horsley, and also on one con-tained in the college stores. In the rabbit, horse, mule, ass,16

15 Willis, ThOmas: Works, ch. xxviii., p. 141, tables 9 and 10.London, 1684.

16 Toussaint, quoted by François-Franck: Comptes-rendus de laSociété de Biologie, 1881, p. 78.

and dog, all the roots from the bulb are intimately united, andthe spinal accessory runs distinctly apart. Undoubtedly in thecat there is a closer adhesion between the spinal accessoryand the lower bulbar roots. I have under the microscopesspecimens of the nerves in a monkey. The nerves werehardened in situ, cut whilst embedded in paraffin, and stuckon the slides before the paraffin was removed. It will be seenthat the spinal accessory nerve of Willis is similar in structureto the hypoglossal, whilst the vagus roots all resemble instructure the white rami communicantes of the sympatheticsystem of nerves. That the vagus roots should resemble thesympathetic rather than other cranial nerves is not sur-prising. In the cyclostomes the vagi include the sympathetic,and extend to the anus. Even in higher mammals there isno sharp boundary between them. The ganglion of thetrunk of the vagus is closely connected with the superiorcervical ganglion, there is an intimate connexion in theanulus of Vieussens, in the cardiac and pulmonary plexuses,and lastly in the abdomen, where the fibres of both com-pletely intermingle. The sections and drawings which Ishow you illustrate the following points. The spinal acces-sory nerve of Willis as well as its separate roots consistsentirely of large medullated fibres collected into a com-pact nerve with hardly any connective tissue and nucleiseparating its fibres. It ii thus similar in structure to,the hypoglossal. Where it is adherent in the jugularforamen to the lowest vagus roots it is separated from themby a distinct connective tissue sheath. It shows no ganglioncells on any part of its course. The size of the nerve beforeit adheres to the vagus roots is the same as when a hasseparated to go to the muscles. There is a gap between the

uppermost of its roots and the lowest of those from thebulb, between which the posterior cerebcllar artery runsbackwards.17 All the vagus roots have the same character.They consist in the main of small medullated fibres with ;a,

few large medullated fibres scattered among the smallerones. Separating the fibres in each root is a considerableamount of connective tissue and nuclei. Moreover, all haveganglion cells upon them. From the roots nearest to thenerves down to the lower end of the bulb the...c is no gap-

between the several roots. It is only as the roots approachthe foramen that they besome ga,ther::d into separateThe lower vagus roots have a number of ganglion cellsthem. In the section of each root there is at )ea"t use

ganglion cell to be seen.ls These roots are gathered uptogether and become applied to the dorsal and anterior partof the spinal accessory, but, as aforesaid, separated from it

by connective tissue. The spinal accessory afterwardsseparates completely. These lower root fibres communicatewith the ganglia on the main vagus trunk, but it does not

completely fuse with the latter until the lower end of theganglion of the trunk of the vagus. The upper and middleroots are collected into two trunks a3 they enter the jugalarforamen. Each has a ganglion upon it, ard in the foramenthese two ganglia become intimately united. Thus, scopical examination distinctly separates these roots fromthe spinal accessory nerve of Wills, and shows that there isno gap in the origin of all the vagus roots, that, they aresimilar in structure, and are intimately connected in or justbeyond the jugular foramen.

LECTURE II.

THE FUNCTION OF THE VARIOUS ROOTS OF THE VAGUS,ESPECIALLY OF THOSE AFFECTING RESPIRATION.

[Mr. Spencer commenced by giving reasons for his choiceof the monkey to experiment on, and gave a short descriptionof his methods. He continued :]

If I place the results hitherto obtained in a tabular form,it will show the chief functions of the vagus nerve rocts inorder from above downwards ; but this order must be taken-in a very general sense. There is, as I have shown, no gapin the nerve roots coming from the bulb. It is, therefore,very easy for the electrical current to spread or for injury tobe done to adjacent roots in the attempts made to divid ovseparate them. Even if such a division into upper, middif,and lower vagus roots be granted, yet different observers willnot make exactly the same divisions. With all due allowance

17 Claude Bernard: Leçons sur le Système Nerveux, vol. ii., p. 2461858.

18 Remak: Frorieps, Neue Notizen, 1837, No. 54, p. 150.

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for this the following table roughly expresses the resultshitherto obtained :—

--

Table of the Ftrmctions of the Vagus Boots.19

The fibres which come from the lung enter through thehighest roots, for the division of these roots produces the samechanges on respiration as does that of the vagi in the neck.The first transverse section across the bulb which involvesthe respira,tory centre has also this effect. If these fibres bestimulated when anœsthesia is slight the effect is an excita-tion of respiration. Should the stimulus be greater there is atendency to arrest in inspiration or over inspiration. Excita-tion of the middle vagus roots in not too deep a stage ofanaesthesia produces cough, in a deep stage arrest in expira-tion. No doubt if a stronger current be employed in amonkey completely ansesthetised, arrest in expiration can beobtained from any of the vagus roots, yet the middle rootsalways arrest with the weakest stimulus. Stronger currentstend to spread and are therefore a source of fallacy. If the

proximal end of the middle roots be excited the same arrestin expiration occurs as when the fibres are stimulated incontinuity. When the distal end is excited after division thelarynx is closed by the adduction produced, and thus therespiration is rendered slow and laboured as by excitation ofthe recurrent laryngeal nerve itself. The weakest currentaffects the cardio-inhibitory fibres. In the monkey a currentwith the secondary coil 16 em. distant from the primaryhas a greater influence on the heart than the excitation ofthe vagus in the neck with a current 8 cm. away from theprimary coil. Those fibres which most readily inhibit theheart are the lower roots of the vagus.

ON THE INTIMATE STRUCTURE OF THE CENTRE OF THEBULB.

It is chiefly by experiments such as those just describedthat our knowledge has been extended with regard tothe physiology of the bulb itself. The nature of theexperiments made upon the bulb have been chieflycutting operations, and therefore liable to produce com-plications. Thus Flourens and Laborde 20 found thatan animal could be instantly killed by removing the ’’,layer of grey matter at the calamus scriptorius, whichis exposed by the separation of the posterior mediancolumns of the spinal cord. This " noead vital" experimentmust, however, produce its result through neighbouringstructures, for the bulb and upper part of the spinal cordcan be divided down the middle line, 21 including the calamus,without arresting respiration on either side. Other experimentshave been equally contradictory, the "intermediary bundle, "22the "ascending root of the ninth and tenth nerves," 23 twogroup3 of cells 24 nearer to the middle line than the hypoglossalroots, the "dorsal nucleus" of the pneumogastric, 25 a cir-cumscribed zone in the formatio reticularis lateralis26 external

19 (Early.)—Bischoff: De Nervi Accessorii Willisii Anatomia et Physio-logia Commentatio, p. 94. Darmstadii, 1832. Claude Bernard: Loc.cit. Waller: Gazette Médicale, 1856, p. 420. Chauveau: Journal dePhysiologie, 1862, tome cxci. (Recent.)-Beevor and Horsley: Brit.Med. Jour., vol. ii. 1888, p. 220. Semon and Horsley: PhilosophicalTransactions, 1890, p. 187. Grabower: Archiv fur Laryngologie undRhinologie, 1894, Band ii., p. 143. Grossmann: Sitzungsberichte derWiener Akademie der Wissenschaften, 1889, Band xcviii., pp. 385, 466.Rhéthi: Ibid., 1892, p. 381 ; 1893, p. 201. Grossmann: Pflüger’sArchiv, 1894, Band lix., p. l. Kreidl: Ibid., p. 9.

20 Loc. cit.21 Volkmann : Wagner’s Physiologie, 1846. Band i., p. 391.

22 Longet: Archives Générales de Médecine, 1847, tome xiii., p. 377.23 Giercke: Centralblatt für die Medicinischen Wissenschaften, 1885,

p. 591. 24 Mislawsky: Ibid., p. 465.25 Holm, quoted by Gad and Marinesco.

26 Gad and Marinesco: Comptes-rendus de l’Académie des Sciences,1892, tome cxv., p. 444.

to the hypoglossal roots have each in their turn been claimedas the essential seat of automatic respiratory movement. In

young animals 27 the roots of the nerves going to respiratorymuscles are supplied from both sides of the bulb, so that ahemisection at the upper end of the cord causes only atemporary or slight impairment of respiratory movement onthe side of the lesion so long as the origin of the phrenicnerve is not injured. In order to avoid the complications pro-duced by injuring the bulb I have made a number of observa-tions on the excitation of different points of the floor of thefourth ventricle. The floor was exposed by removing aportion of the occipital bone and then raising the middlelobe of the cerebellum or actually removing it in part orwholly. The results have served to confirm those justdescribed on the vagus nerve. At the level of origin of theupper vagus roots respiration may be excited and over-inspira-tion may be produced. At tht level of the middle roots,if the animal be in deep anaesthesia, there is always arrest inexpiration, behind this at the level of origin of the lowestvagus roots cardio-inhibition.

The cerebrum and respiration.-Whilst experimenting uponthe fourth ventricle I found that respiration could be affectedby excitation of the floor far above the roots of the vagus.Recognising that this must be due to the stimulation of thefibres descending from the cerebrum to the respiratory centreI turned to the research which is described in the last numberof the Philosophical Transactions under the title of "TheEffect produced upon Respiration by Faradaic Excitationof the Cerebrum in Monkey, Dog. Cat, and Rabbit. "28 Nodefinite results had been obtained by previous observers, theanimals having been either too deeply or insufficientlynarcotised. Munk29 alone had some results which as faras they go were confirmed by my own. Christiani 30 andalso Martin and Booker 31 found respiration to be influencedfrom the mesencephalon, especially at the side of the hinderend of the third ventricle and the aqueduct of Sylvius. Theysupposed their experiments to show respiratory centres in themesencephalon, but I have no doubt that they stimulated thetracts leading from the cortex to the respiratory centre in thebulb which I am about to describe. As a result of a numberof experiments upon the four species of animals-cat, dog,rabbit, and monkey-by excitation of the cerebral cortex,and the surfaces of cerebral sections carefully made in avertical plane backwards to the bulb, I found four differentresults, each obtainable from a distinct area on the cortex,and traced each back along a definite line. These four effectsI will proceed to illustrate by photographs and tracings, andit will be seen that they are such as can be produced uponthe respiration by means of the will. (a) The first effect isthat which leads to a diminution of action on the part ofthe respiratory centre, and finally to an arrest. Slowingconsisted in a definite diminution of the rate of respira-tion during the time of the stimulus, and if the strengthof the stimulus were increased there was an immediatearrest of the rhythm. This arrest might last for a minuteor more if the stimulus were strong enough. Generallyrespiration started again at the previous rate immediately onthe cessation of the excitation. If the stimulus were insuffi-cient it might only momentarily arrest it. The cortical areafrom which this result was obtained is situated upon thefrontal lobe just outside the olfactory tract, anterior to thepoint where it joins the temporo-sphenoidal lobe, as indicatedby the crossing of the Sylvian artery. The same result wasobtained along the line of the strand of fibres known as theolfactory limb of the anterior commissure. After decussationin the latter structure the tract continued backwards by theside of the infundibulum into the red nucleus below andexternal to the aqueduct in the plane of exit of the thirdnerve. That the strand of fibres on either side decussates inthe middle line may be shown by making hemisections back-wards until the anterior commissure be reached. Before thehemisections have reached the level of the anterior com-missure the cortex of the sound hemisphere still retainsits power of arresting respiration. When, however, thehemisections pass the anterior commissure the cortex ofthe sound side loses its excitability, but arrest can thenbe obtained from the mesial cut surface of the anterior com-missure. The fibres affecting respiration are thus excited just

27 Langendorff: Archiv für (Anatomie und) Physiologie, 1881, p. 78;1893, p. 397.

28 Spencer : Philosophical Transactions, 1894, vol. clxxxv., p. 609.29 Munk: Ueber die Formationen der Grosshirnrinde, p. 614.

Berlin, 1890.30 Christiani : Zur Physiologie des Gehirnes, chap. i. Berlin 1885

31 Martin and Booker : Journal of Physiology, vol. i., p. 370.

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after decussation. The character of the arrest varied indifferent stages of anœsthesia-the deeper the anesthesia thegreater the tendency to arrest in expiration ; in lighteranœsthesia arrest was either in full inspiration or in overinspiration.

(b) The other effects found have the tendency to increasethe action of the respiratory centre in the medulla. The

respiratory rate may be greatly accelerated, but what is

gained by acceleration may be partly lost by diminution inamplitude. This diminution does not neutralise, however,the increase of rate, because apncea may be produced in thisway. In an imperfectly anaesthetised animal any excitationof a sensory surface may tend to cause some acceleration,but the tracings in my animals show that this is a verymarked acceleration of the rate unaccompanied by anyirregular movements. The cortical area on which the

greatest acceleration can be obtained lies around the upperend of the infra-orbital sulcus in the dog and cat. Inthe rabbit the point is marked by a vessel which comesup between the mesial edge of the hemisphere and thefalx cerebri, and then turns out over the convex surface,grooving the surface of the cortex in a line which

suggests correspondence with the crucial sulcus in thecat and dog. Marked acceleration is obtained on eitherside of the vessel at the edge of the hemisphere. The

position is similar in the monkey-viz., about the sulcus X.’the acceleration may be followed back through the lenti-cular nucleus, where it borders on the outer ventral portionof the internal capsule. The strand runs at first externallyand then ventrally to the motor portion of the internal

capsule and so reaches the tegmentum. The lines from thetwo sides meet in the interpeduncular grey matter at thelevel of and just below the plane of exit of the third nerve.A hemisection in front of the exit of the third nerve does notremove the acceleration effect from the cortex of the remain-ing hemisphere. On the other hand, a hemisection imme-diately in front of the pons does so.

(c) Another increased action of the respiratory centre canbe obtained, resembling that made by snuffing. The four

species of animals reacted in a similar way. The animalfirst made an over inspiration, then several sharp over

inspirations were super-imposed and followed the primaryone. These over-inspiratory jerks were peculiar in followingone another at regular intervals in a rhythmic manner, andnot ceasing exactly at the same time with the stimulus, one,two, three, or more over-inspirations taking place after thecessation of the stimulus. To this movement I have giventhe term over-inspiratory clonus. Each over inspiration wasfollowed by a sharp expiration, during which the thorax didnot reach the position of equilibrium-that is, there was noaction of expiratory muscles. This effect was obtained fromthe mucous membrane of the upper part of the nose,from the olfactory nerves, bulb, and tract. On applyingthe stimulus in a line backwards along the olfactory tract,this snuffing movement was traceable to the uncinate con-volution of the temporo-sphenoidal lobe. From the uncus it

passed behind the optic tract to the crus, and thenceobliquely inwards underneath the crusta. Thus the tract oneach side converged to meet in the middle line at the upperborder of the pons. Excitation of this point was the onlyplace on the section where this result could be obtained.

(d) The fourth effect which can be obtained from the surfaceof the cerebrum is a widely generalised one, because it canalso be got by the excitation of any sensory nerve. Thechest assumes a position of over inspiration by means of thetonic contraction of the extraordinary muscles of inspiration,but the rhythmic movements of the ordinary muscles con-tinue in a regular manner. If an excessive stimulus be usedthe over-inspiratory spasm produces a pseudo-arrest bymasking the rhythmic movements. But the latter can beseen to continue, only obscured by the tetanic spasm. Thesensory motor area on the cortex and the descending motortract specially yield this result. It can also be got from thefifth nerve and from the sciatic after complete removal of thecerebrum at the level of the tentorium cerebelli.

SUMMARY OF THE AFFERENT CONNEXIONS OF THERESPIRATORY CENTRE.

Sensory nerves of all kinds tend to excite the respiratorycentre in the direction of inspiration, any acceleration of therate being due to the will, and, therefore, not obtainable inanœsthetised animals. If the stimulus be too strong thethorax is driven into an over-inspiratory spasm, but therespiratory rhythm is here not really arrested except by the

spasm of other muscles counteracting those of ordinaryrespiration. Such inspiratory spasms are seen in auy wide,’excitation of the skin, such as by cold water, tickling, and inthe first stage of drowning. When the spasm comes to anend in the last case bubbles of air escape from the mouth.This inspiratory 32 spasm in the first stage of drowning is notdependent on the will, for it takes place in a narcotisedanimal; nor is it due entirely to the cold, for it takes placein water at the temperature of the blood ; neither is it whollydue to inhibition from the larynx, for respiration is arrestedin rabbits although a tube may have been previously placed °in the trachea and its free end kept above water. The’vagus nerve in the neck contains inspiratory fibres which ’enter the bulb through the upper roots. The centre of’the sensori-motor area of the cortex is likewise influencedin the same way-e,g., in epileptic fits. This inspiratoryinfluence through sensory nerves is entirely lost in deepanaesthesia, so that the strongest current applied, for in-stance, to the fifth nerve has no effect on respiration. The

respiratory centre can be inhibited, its rhythm slowed andarrested in expiration, and the chest remains motionless inthe position of equilibrium. This takes place by electricalexcitation of the fibres entering by the middle roots of thevagus, by excitation of an area on the cortex cerebri and:of a tract connecting this area with the medulla, and byexcitation of the floor of the fourth ventricle. The’

deeper the anaesthetic the more readily is the inhibition’obtained uncomplicated by inspiratory influence. Acceleration of the rhythm apart from the influence of the willof the animal is far more marked on the cerebral cortex’and on a tract leading down to the bulb. Probably it isdifficult to get such acceleration from the floor of thefourth ventricle on account of the simultaneous exci-tation of inhibitory influences. From the nose two forms’of excitation may pass back to the respiratory centre--an inspiratory tonic effect through the fifth nerve and an.inspiratory clonic effect through the olfactory nerves andbrain. No inhibition of respiration was obtained from thenose in anaesthetised animals. The arrest of respirationwhich other observers have noted has happened in animals.fully awake. When tobacco smoke or chloroform is blowninto the nose of a rabbit it holds its breath. The will isthe cause of the arrest in this and other powerful sensations.which can be perceived by the animal.

Uver-action of the respiratory centre.-The respiratory,centre can be stimulated by changes in the composition of the:blood supplied to it: (1) by excess of carbonic acid ; (2) by’defleiel,cy of oxygen; (3) by an increase of oxygen, especiallyif the centre be failing ; (4) by an increase in the tem-

perature of the blood ; and (5) by the products of muscularmetabolism.

1. An excess of carbonic acid gas in the air breathedbegins to cause hyperpncea when it reaches to 3’5 per cent.33.This is about the amount contained in expired air. In aircontaining about 5’5 per cent. breathing has to be a,s.

deep as possible, and at double the normal rate. If the<amount of carbonic acid gas be greater distress becomes.marked when the carbonic acid gas amounts to 10 per-cent., even although there be an ample sapply of oxygenIf, however, the carbonic acid be mixed with oxygen-an,,air in which oxygen has not been diminished-7 per cent. ofcarbonic acid can be for a time inspired without harm. The,

hyperpncea thus excited by the carbonic acid introduces.sufficient oxygen.

2. Reduction of oxygen to 12 per cent. excites respiration,.but not to the extent of the corresponding increase in,carbonic acid. Marked byperpnoea is caused with 9 per cent.of oxygen. When reduced to 7 or 6 per cent. there is a

tendency to loss of consciousness, paralysis of limbs, andimpairment of breathing. We are well acquainted with thisdiminution of oxygen in the course of the administration foran&oelig;thesia of nitrous oxide or nitrogen gas.

3. An increase of oxygen tends to stimulate a failingrespiratory centre. The administration of air restores the

respiration to the normal ; oxygen in a more concentrated’form prcduces general excitement and stimalates the respi-ratory centre so much that apnoea does not occur.

4. A most powerful stimulant to the rate of rhythm and tOIits depth is a slight increase in the temperature of the bloodflowing through the bulb. Either the blood in the carotid

32 Falk: Archiv f&uuml;r (Anatomie und) Physiologie, 1869, p. 239.33 Haldane: Proceedings of the Physiological Society, 1894. Pro-

ceedings of the Royal Society, 1895. Haldane and Lorrain Smith:Journal of Pathology and Bacteriology, 1893, vol. i., p. 168.

470

may be warmed or the animal may be overheated.34 Thus in ’an experiment when the temperature in the vagina or rectum was 39 ’8&deg; the rate was 4Z per minute, at 41 -1&deg; C. 142. 35 A dog with a rectal temperature of 39 2&deg; C. and a respiratory rateof 20 per minute was placed in a chamber at 73&deg; C., when therectal temperature rose to 408&deg; C., the respiratory rate quick-ened to 50 per minute, more than double the amount of airpassing in and out per second. During this acceleration byheat the animal cannot be made apnoeic, and moreover showsgreat resistance to narcotic poisons. Thus morphine or

chloral may be given in a sufficient dose to lower the rectaltemperature and impair the respiration. On the applicationof heat sufficiently to raise the rectal temperature 1&deg; C.above the normal the respiration rate may be doubled.36

5. The centre is further excited by the products of musclemetabolism. Afferent stimuli being excluded by division ofthe spinal cord, the tetanising of the muscles of the hindlimb causes an increase in the respiratory rhythm, whilstthe oxvgen and carbonic acid in the blood remain normal.Thus during work increased respiration keeps the amount ofoxygen and carbonic acid in the blood normal. In the horsethe amount of oxygen taken in and the carbonic acid givenout is enormously increased during movement, the respiratorvquotient not altering as compared with that during rest.38The walk increases the respiratory interchange about two anda half times, the trot five times that of the rest ; in thegallop ten to twenty times more air is taken in and given out.39This enormous increase in respiration is connected with thediminished alkalinity of the blood 40 from an excess of lacticacid produced by muscular activity. This acid acts as adirect excitant to the respiratory centre of the rabbit.41The carbon dioxide diminishes the alkalinity of the blood,and the excitation which it causes may be an instanceof the same kind-viz., the excitation of the centre by aweak acid. In diabetic coma not only lactic acid butacetic and oxybutyric acid 42 have been found in the blood.When sugar in sufficient quantities to affect a dog is injectedlactic acid is found in the blood. Diabetic coma and rapidtissue changes in fevers may, therefore, have a double- excitatory influence on the respiratory centre by diminishing- the alkalinity of the blood, as well as by raising its temperature.

Diminished action of the respiratory centre. -The action ofthe respiratory centre may be lowered : (1) by diminution inthe amount of carbon dioxide in the blood, provided thatthis is not neutralised by excess of oxygen, or of tempera-ture, or of the products of metabolism-this diminutionmay be due to removal by forced artificial respiration or by adiminished production of carbon dioxide ; (2) by excess ofcarbonic acid (asphyxia) and poisons (anaesthetics &c ) ;and (3) by impairment of the circulation through the centre,whether by failure of the heart, by vaso-motor paralysis, or

by increase of intracranial pressure.Apn&oelig;a.43-Forced artificial respiration by removing more

carbonic acid from the pulmonary alveoli causes the bloodto become of a more scarlet hue. If this be done withair at the temperature of the room the animal is rapidlycooled. Long apnoeic pauses are obtained when the centrehas been depressed by the cooling. After artificial respi-ration for one minute a pause may follow for twenty-6ve to thirty seconds, after artificial respiration for twominutes a pause of two minutes, or for ten minutes afterartificial respiration for half an hoar. At the end of the

apnoea the blood has lost its bright colour and natural

breathing begins. After making a number of deep respira-tions the length of time during which a man can hold hisbreath can be extended from a quarter of a minute to oneminute or more. The conditions, however, are not exactlythe same as in experiments upon animals, for whilst holding’the breath expiratory muscles gradually compress the air inthe lungs and so favour the entrance of oxygen, as in theCetacea. (See below.) When we turn to other conditions in

34 Ackermann: Archiv fur Klinische Medicin, 1867, Band ii., p. 357.Goldstein: W&uuml;rzburger Verhandlungen, 1872, p. 156.35 Anderson: Dublin Journal of Medical Science, 1880, vol. lxx., p. 269.

36 Brunton: Journal of Anatomy and Physiology, vol. viii., p. 332.Brunton and Cash: Ludwig’s Festschrift, 1887, p. 149. Wood andCerna: Journal of Physiology, 1892, vol. xiii., p. 870.

37 Geppert and Zuntz : Pfl&uuml;ger’s Archiv, 1888, Band xlii., p. 189.38 Zuntz and Lehmann : Journal of Physiology, 1890, vol. xi., p. 396.

39 Smith, F.: Ibid., p. 65.40 Lehmann : Pfl&uuml;ger’s Archiv, 1888, Band xlii., p. 284.

41 Jacquet: Archiv fur Experimentelle Pathologie und Pharmacologie,1892, Band xxx., p. 11.42 Harley : Proceedings of the Royal Society, 1893 and 1894.

43 Rosenthal: Hermann’s Physiologie, Band iv., Theil ii., p. 264.Ewald: Pfl&uuml;ger’s Archiv, 1873, Band vii., p. 575.

which apncea occurs-viz., the apnoea of the f&oelig;tus, thatexisting during hybernation, or in those apparently dead-wemust take into consideration the important relations whichthe central nervous mechanism of the respiration has withthat of the heat regulation or internal respiration,44 and thatof the vaso-motor mechanism. The mechanism of heatregulation in warm-blooded animals is intimately con-

nected with respiration, for the excess of CO2 given offin the production of heat must be got rid of. But beforebirth and for a variable time after birth the animal is moreor less cold-blooded-i. e., has not- yet developed a completeheat-regulating mechanism.45 Thus new-born mammals suchas rats, mice, and puppies react like cold-blooded animals,their temperature sinks towards that of the surroundingmedium, and at the same time there is a corresponding fall inthe amount of CO2 given out. Soon after birth they gain aheat-regulating mechanism, which becomes so established thatwhen placed in an atmosphere colder than themselves theygive out more CO2 and maintain their temperature. Thus inyoung blind mice about three days old on a fall of tempera.ture from 30&deg; to 20&deg; C. there is a lessening in the dischargeof C02 within thirty minutes to about one half ; a few dayslater, on the other band, there is a rise in the CO2 given outunder similar circumstances. A chick in the egg reacts likea cold-blooded animal, its temperature falling with that ofthe medium and less CO2 being given out. It reacts like awarm-blooded animal after hatching, and it has then controlover its muscles and is able to run about. A pigeon whenhatched is blind, naked, and helpless, one of the parent birdsis constantly sitting over it and feeding it, and when exposed tocold it reacts like a cold-blooded animal.The human foetus46 when born, especially if before

term, rapidly cools if exposed to a medium much lowerthan that of the blood, less CO2 is produced, and therespiratory centre may not be excited. Hence the answerto one of the questions put by Harvey : Why does a fmtuaborn in its membranes not breathe? Being like a cold-blooded animal little CO2 is produced, and the circula.tion passing by the ductus arteriosus is not obstructed in

attempting to pass through the lungs. Life-that is, thecirculation-has been said to last in a new-born child,especially before term, for fifteen hours without any apparentrespiration. These infants may show after death evidencesof inj ary such as ecchymosis &e.47 On the other hand, thenormal respiratory centre at term is sufficiently excitable tobe stimulated by any increase of carbon dioxide above theamount existing in the circulation of the mother. If theabdominal aorta of a pregnant animal at term be compressedthe foetus begins to gape and inspire in the liquor amnii. Asin apnoea produced by inflation, so also in the apnoea of thef&oelig;tus a sufficient excitation to the skin may produce oneinspiration, but is not the cause of the commencementof rhythm. An apnoeic foetus responds to external stimu-lation by an inspiration, whereas one which has become

asphyxiated does not. Whilst under normal circumstancesan increasing venosity of the blood is a sufficient stimulusto the centre, yet if the centre be weakened from any causeit may fail to respond to the venous blood, therefore death

may occur without any attempt at breathing. The circum-stances of a long labour by hindering the circulation of thefoatus may gradually impair the centre, whereas if the

venosity of the blood comes on rapidly without any pre-liminary exhaustion of the circulation a f&oelig;tus must inspirewhether before or after birth.When the foetus has once breathed it must continue to do

so. Oxygen, entering with the first breath, raises the excita-bility of the centre and at the same time stimulates internalrespiration, whilst the distension of the lungs from theirprevious atelectatic state diverts the circulation throughthem. After the first breath an arrest of respiration placesa mechanical hindrance in the way of the circulation, whichhas now to pass through the lungs. Further also, the moreactive metabolism increases the amount of CO2 given off.Hence the answer to Harvey’s second question-why itcannot dispense with respiration when once it has breathed-is to be found in the increased excitability of the respiratorycentre and the larger amount of CO2 given off from thetissues. Instead of apnoea asphyxia then occurs. Whilstin an apnoeic f&oelig;tus an external stimulus may cause it to take

44 Hale White : Brit. Med. Jour., vol. ii. 1894, p. 1093.45 Pembrey : Proceedings of the Physiological Society, 1894 and 1895.46 Preyer: Specielle Physiologie des Embryos. Leipzig, 1885. Engstr&ouml;m

Skandinavisches Archiv f&uuml;r Physiologie, 1891, Band ii., p. 158.47 Bardinet: Gazette M&eacute;dicale de Paris, 1864, p. 688.

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one inspiration and so introduce oxygen, this method must

compare unfavourably with artificial respiration, in whichthere is not the danger of mechanical injury. Exposure in acold room or the application of cold water, by lowering thetemperature, impairs the centre. In a state of asphyxia thefcetus will not respond to external stimuli, and then artificialrespiration is the sole remedy, aided always by externalwarmth-an important adjanct-applied by a hot bath orespecially to the neck.In hybernating animals the absence of respiration is

accompanied by a great fall in the production of carbondioxide. They become cold-blooded, the temperature fallingalmost to that of the air; at the same time the circulationbecomes very feeble. A hybernating marmot or dormousecan live in an atmosphere of C02, in which a bird or ratperishes instantly.4s The respiratory centre is in them in astage of apncea, a marmot pinched during hybernation givesan inspiration. A raising of the temperature of the mediumexcites respiration, the animal recovers its normal tempera-ture, and circulation and muscular activity.A rapid production of carbonic acid in a warm-blooded

animal produces asphyxia, paralysing the respiration. Twoinfluences may delay the onset of asphyxia-a large amountof blood holding a good stock of oxygen, and an increasedtension of the oxygen in the lung favouring absorption.The respiration in the Cetacea 49 forms an interesting examplein this respect. In them internal respiration must beenormous to maintain a body temperature of 37&deg; C., andthey are very active animals. They are characterised byhaving a circulatory apparatus and an amount of blood muchin excess of a land animal of the corresponding size. Sealscan remain under water for five minutes and whales for amuch longer period, yet the time they spend at the surface isexceedingly short. A dolphin at rest in an aquarium breathedthree times a minute. It began with a rapid forced expira-tion through the vent for one second, the return to the positionof equilibrium and an inspiration lasted another second, andthis was followed by a pause of eighteen seconds. This

pause is really an inspiration during which, the vent beingclosed, the air is subjected to pressure from the chest walls.In this way oxygen can pass from the lungs into the bloodduring the time the animal is under water. The excessiveamount of carbon dioxide which has collected during thepause whilst the animal is under water is got rid of by theforced expiration. It is by imitating this respiration of theCetacea that men can dive and remain under water in activemovement. To show the value of the store of oxygen in a largeamount of blood Paul Bert 50 compared the behaviour of a fowlplunged under water with that of a duck. A fowl plungedunder water is soon distressed, the inspiratory inhibition

gives way, bubbles of air escape, the bird loses consciousness,and falls on its flank with a loss of the corneal reflex in abouttwo minutes. It makes a series of inspirations, the lastaccompanied by rigidity, and in about three minutes is dead.The duck can remain under water, simply struggling to

escape, for seven minutes after immersion without expiring.Its heart beats much slower, and may even fall in rate from100 to 14 per minute, showing that carbonic acid is collecting,but the conjunctival reflex remains, and consciousness is

preserved. The want of oxygen is not felt for seven, ten, oreven fifteen minutes, then the animal loses consciousnessand its reflexes, lets air escape, falls on its side, makes someinspirations, becomes convulsed, and dies. The behaviouris the same in the two birds, when the trachea is clamped,the fowl dies within three minutes and the duck lives fromeight to sixteen minutes, so that the delay cannot be attri-buted to the custom of diving on the part of the duck. Thelungs and air sacs are similar in the two birds. Weight forweight, however, Paul Bert found the duck to contain one-third more blood than the fowl. If about half the bloodwere first taken from a duck it died as quickly under wateras a fowl.

48 Spallanzani: Memoirs on Respiration, p. 305. Senebier, 1805.49 Jolyet: Archives de Physiologie, 1893, p. 610,50 Paul Bert: Le&ccedil;ons sur la Respiration, 1870.

THE governors of the Farringdon GeneralDispensary held their annual meeting on Feb. 12th ab theonces in Holborn, Mr. Lacy, the treasurer, presiding. Thepatients during last year numbered 24,286. The total incomer the year was &pound;730. The Hospital Sunday Fund and theHospital Saturday Fund made grants of &pound;43 and &pound;11 respec-tively, and a donation of &pound;25 was received through AldermanTreloar. The balance in hand at the end of the year was &pound;109.

Lettsomian LecturesON THE

COMBINATIONS OF MORBID CONDITIONS OFTHE CHEST.

Delivered at the Medical Society of London on Feb. 18th, 1895,

BY FREDERICK T. ROBERTS, M.D.,F.R.C.P. LOND.,

PROFESSOR OF MATERIA MEDICA AND THERAPEUTICS AT UNIVERSITY

COLLEGE ; PHYSICIAN AND PROFESSOR OF CLINICAL MEDICINE ATUNIVERSITY COLLEGE HOSPITAL; CONSULTING PHYSICIAN TO

THE BROMPTON HOSPITAL FOR CONSUMPTION ANDDISEASES OF THE CHEST.

LECTURE III. ’

CLINICAL LESSONS; INVESTIGATION OF CHEST CASES.Symptomatology.

MR. PRESIDENT AND GENTLEMEN,-Although in my lastlecture I placed physical examination in the forefront inrelation to the investigation of combined chest cases, I by nomeans wish to give it undue prominence. On the contrary, -Ifeel it necessary to utter a protest against a practice which isnot at all uncommon-namely, to be content with finding outin this way what physical changes or conditions, if any, exist,and looking at the case solely from this standpoint, estimatingits importance simply by the presence or absence and the.degree of such changes. This is a dangerous error, and R.row urge the imperative necessity of an intelligent study ofthe symptomatology in every instance, and of endeavouringto understand the phenomena complained of or observed intheir relation to the morbid conditions present. I say " study’ "

advisedly, as distinguished from a mere enumeration of chestsymptoms, which is of little value, as it may apply equally toany number of thoracic cases which are essentially differentin character.

I have already pointed out that there may be practicallyno symptoms even when very pronounced and complicated,morbid changes are present in connexion with the chest.This negative aspect, however, must not be overlooked ; forit may be highly significant as indicating the pathological.nature of these changes, showing that they are not, at anyrate, of a serious character in themselves, and that they dsnot materially interfere with the important thoracic contents.But I have now to deal with chest symptoms from their morepositive aspect; and I am anxious to indicate as clearly as pos-sible certain points which, in my opinion, are of the greatestconsequence in relation to the subject which forms the basis ofthese lectures. In the first place, it must be remembered that.the thoracic structures are closely related to each other,.anatomically and physiologically, as well as pathologically,and it is a great mistake to separate too definitely the sym,ptoms associated with particular organs. It must be familiarto any intelligent clinical observer that there is no actual lineof demarcation between the symptoms due to pulmcnary andcardiac diseases respectively, and when we have to deal withcomplicated conditions any distinction of this kind becomesabsolutely impossible and mischievous. Under these circum-stances it is imperative that they should be studied on a .thoroughly comprehensive basis, in order to understand theirpractical relations and significance. In an acute or suddencase the study of local chest symptoms is of the utmost,importance, and may reveal the presence of conditions or dis-turbances which cannot possibly be determined by physicalexamination, especially when the state of the patient doesnot allow such examination to be carried out efficiently. Thephenomena, even of individual acute diseases, as describedin text-books, are by no means always typical; but when wehave to deal with the various combinations to which I havepreviously referred, they become still less characteristic. Itis under these circumstances that the study of the symptoms.becomes particularly instructive. The severity and charactersof pain and other morbid sensations, the kind of disturb-ance of breathing and the various noises associated therewith,the peculiarities of the cough and expectoration, and other-symptoms, are all worthy of attention, and often reveal.

important features of the case. The varieties of so-

called "dyspnoea" demand special study, for they are often,,most significant, and we may have to found our diagnosis.