917

TREATMENT OF SCABIES

To the Editor of THE LANCETSiR,-Seeing that Dr. Kingston’s excellent article

on this subject in THE LANCET of Oct. 12th confirmsthe experiments which I myself made about 20 yearsago, but failed to publish, I feel that I must now

support his findings, and congratulate him on drawingattention to the fact that whereas the " sulphurtreatment " has been handed down from one text-book to another as a so-called cure for this condition,this is far from being the case as is so commonlythought. The " cure while you wait system,"as used in some hospitals, where the patient is givena sulphur bath, thoroughly scrubbed with a nail-brush and sulphur ointment applied, is I am sure

doomed to failure. Much may depend upon theefficiency of the scrubbing and thereby opening upthe burrows made by the acarus, but it must not beforgotten that if only one of these escapes (and Iam convinced that many more than this must do so),and if only one acarus is left behind under the skin,eggs will be produced at the rate of 2 or 3 a day for14 days. The acarus may lay as many as 50 eggs.These take 14 days to hatch, so that it would takeabout six weeks before the last eggs are hatched.This surely is the cause of so many recurrences afterso-called immediate cures.My contention is that every case treated should be

examined weekly for at least six weeks before onecan affirm that a cure has been effected, and yethow seldom is the trouble taken to carry out thisroutine. In a large hospital, such as a mental

hospital, it is practically impossible to eradicatethis trouble unless some such routine is adopted.

In support of the findings which Dr. Kingston hasrecorded I would add that I have found the acarusin a burrow after the patient had had the recognisedsulphur bath treatment, followed by daily applica-tions of sulphur ointment for 14 days. I have alsofound the live acarus in the burrow under the skinof a patient who had had the sulphur bath treatmentfollowed by applications of sulphur ointment twicea week for four weeks, and in many cases after

shorter periods of similar treatment. Further, ina wax cell on a slide under a cover-slip I found thatthe acarus would live for 24 hours immersed in water,48 hours crawling about over sulphur ointment, andas long as seven days in a cell such as described withnothing else in it.

I am naturally pleased to see that Dr. Kingstonhas taken the trouble to make somewhat similarinvestigations and that his results so closely agreewith my own. But surely it is time that medicalstudents were taught that the sulphur bath andointment, as described in most text-books, is not acure, and that repeated trials and examinations mustbe made to prevent the relapse and further spread ofthis condition, which once left unrecognised andimproperly dealt with becomes a source of untoldtrouble in any large institution.

I am, Sir, yours faithfully,

Oct. 15th.

R. EAGER,Medical Superintendent, The Hospital,

Exminster.

GERMICIDAL PROPERTIES OF MERCURYPREPARATIONS

To the Editor of THE LANCETSIR,-In the annotation entitled Skin Disinfection

in your last issue (p. 838) you refer to the well-knownfact that the germicidal properties of mercury prepara-tions as determined. by different methods vary

enormously. We think that the following simpleexperiments throw a great deal of light on the causesof the discrepancies.When the carbolic-acid coefficient of mercury prepara-

tions is determined, a loopful of the bacterial culture,after contact with a known concentration of the mercurycompound, is removed after a known interval of time, andis subcultured into a given quantity of nutrient broth.If no growth subsequently occurs in this broth it has beenassumed that the bacteria in the treated culture werekilled when the loopful was removed. Usually this

assumption is correct, but in the case of mercury prepara-tions the assumption is purely fallacious. The refusalto develop is due to the bacteriostatic action of the

accompanying mercury salt carried over with the loopfulinto the broth. If instead of plain nutrient broth, brothcontaining 0’2 c.cm. of a sterile 5 per cent. solution ofsodium sulphide per 5 c.cm. of broth is employed, anentirely different picture of the facts is obtained. The

sulphide inactivates the mercury which is carried over,and the supposedly dead germs are found to be alive andunharmed. The differences between the real and the

apparent germicidal properties of a few mercury prepara-tions are seen in the following Table :-

Mercury Real carbolic- Apparent carbolicpreparation. acid coefficient. coefficient.

Mercuric chloride.. 0’15 .... 800Mercuric cyanide.. Less than 0’1 .... 25Mercuric iodide 7 .... 1300N.B.-The mercuric chloride in the strong solutions that were

necessary was dissolved with the help of sodium chloride andthe mercuric iodide with the help of potassium iodide. Theactual coefficient of mercuric cyanide could not be determinedbecause a 10 per cent. solution (which is actually a supersaturatedsolution at 180 C.) failed to kill the bacteria after 10 minutes’contact.

We think we can now give a reasonable explanationof the germicidal failures of mercury preparationsunder clinical conditions. For instance, the Depart-mental Committee of Maternal Mortality and

Morbidity in their final report (1932, p. 113) showedthat a 1 in 1000 solution of mercury perchloride didnot kill haemolytic streptococci on the hands nor didit prevent reinfection after a time. From the abovetable it will be seen that mercury perchloride is actuallya much weaker germicide than pure carbolic acid,and a 1 in 1000 solution is a very feeble one bacteri-cidally. When such a solution is applied to the skin,the mercury compound tends to combine slowlywith the excretions of the sweat glands to forminsoluble compounds, and as the bacteria have notbeen killed they can subsequently be removed in theliving condition. It is only when some solubleuncombined mercury compound is removed with thebacteria that fictitious results are obtained.The germicidal ineffectiveness of soluble mercury

compounds in the presence of pus and blood is toowell known to require special comment.

WA are Sir- vours fa,ithfnllv_

Hull, Oct. 15th.

W. C. REYNOLDS,S. N. H. STOTHART.

PARIS(FROM OUR OWN CORRESPONDENT)

THE SURGICAL CONGRESS

THE Association Francaise de Chirurgie held its

forty-fourth congress in Paris from Oct. 7th to 12th,these dates being chosen so that it might coincidewith the motor show.

In his opening address, Prof. Gaston Michel, ofNancy, courageously faced the dangers threateningthe medical profession at the present time, as muchfrom within as from without. He pleaded forscientific probity, and a critical attitude towards" too beautiful statistics " and towards those who