A STUI)Y OF THE CUBOID AND OS PERONEUM IN THEPRIMATE FOOT. By T. MANNERS-SMITH, M.A., AM.B. Cantab.,Deetnonost rotor of A utou, il,)b the Uti[ versi(ty of 0(Yu1))ri(1le;Lectcuesr i}& Aitato0ny, Dwvibitn Colleqje.

IN the July number of last year's Journal I published an account ofthe navicular in the human and anthropoid foot. I have selected thecuboid next, since it has both points of similarity and points of strongcontrast to the former bone.

The two bones are markedly alike in those attributes which aredetermined by morphological factors: thus they have both a so-calledsesamoid element in their neitghbourhood.

The two bones are markedly at variance ill respect to thosecharacteristics which are dependent upon mechanical causes: thus thenavicular, from the fact that it remains comparatively long cartilaginousand because a powerful muscle is attached to it, presents considerablediversity of shape. The cuboid, on the other hand, since it is one of theearliest tarsal bones to ossify, is remarkably regular in outline.

The cuboid, too, is interesting in respect to its serial homology. Ineach limb the corresponding bone consists morphologically of carpaliaor tarsalia 4 and 5. In each case it articulates with correspondingmnetacarpalia or muetatarsalia. In each case it has additional elementsin its vicinity-the os peroneum in the lower limb, the os pisiforme andos hamuli proprium in the upper.

The human specimens of cuboid (about 550 in number) were from thecollection of Egyptian bones in the possession of Professor Macalister.The primate bones were derived from specimens belonging to Dr Duck-worth. I have much pleasure in thanking both these gentlemen for theirkindness in providing me with material.

I am deeply indebted to Mr Winfield, of Downing College, for hisggreat care in taking the photographs from which the illustrations wereprepared.

Non-enelatuare.As in umy last paper, I have adopted the terms in use by, or formed

on the plan of, the Basle Convention. The names which I have chosen areas follows:

Mr T. Manners-Sinith

Nomenclature formed on the Model of theBase Convention.

Os cuboides.Cuboides bipartitum.Cuboides secundariusn (Pfitziser).

Os peroneurm or peroneumu (Pfitzner).'ruberositas ossis metatarsi V.

Facies articularis posterior.Facies articularis anterior.

Facies articularis medialis.Facies lateralis.Facies plantaris.Facies dorsalis.

Nomenclature in use in England.

Cuboid.Cuboid divided into two.The calcaneal tullercle when it is pro-

loIiged backwards to articulate withtile astragalus.

Peroneal sesainoid.The tuberosity of the 5th metatarsal bone,

sometimes existing as a separate bone(th(e- bone of Vesalius).

Posterior surface for calcaneum.Anterior surface for 4th and 5th meta-

tarsals.Internal surface.External surface.Inferior or plantar surface.Superior or dorsal surface.

Facies Articnlcari.as 1Posterior.This may be discussed under (ca) the outline of the surface; (b) the

direction of its curvatures; (c) the prominence or otherwise of thecalcaneal process.

(a) The Ottline of the Snrf(tce.-Thomson 1 speaks of it as being semilunarin outline; Morris refers to it as quadrangular, with rounded angles. Inmost cases (217-92 right, 125 left) it agrees with Thomson's description; itis semilunar or half-oval. It has the concavity of the half-moon or the baseof the half-oval directed towards the plantar surface. Of the two ends ofthe crescent, the most prominent is formed by the calcaneal process.

In 97 (51 right, 46 left) specimens it approaches the quadrangular,with rounded angles in most cases. In 69 specimens it is wedge-shaped,with a truncated apex directed towards the inferior external angle. Inthe others not accounted for it was broken.

(b) The Direction of the Curvatu~res.-The posterior surface articulateswith the os calcis by means of a saddle-shaped facet, which is convexfrom side to side and concave from above downwards (Cunningham).It presents a saddle-shaped articular surface for the os calcis (Morris).Thomson's description holds good in the majority of cases; sometimes itis flattened from above downwards. Not infrequently there is a slightconcavity at one side, near the outer end. In four specimens it is convex,in most of its extent, in both diamneters.

(c) The Calcva eat Process.-Cunningham, Quain, and Macalister alldraw attention to this process. The last observer states: "It will be

1 Cunningham's Tcrt-book (ye Al natoy.

398

Study of the Cuboid and Os Peroneum in the Primate Foot 399

observed that there is a posterior calcaneal process of the cuboid, whichundershoots the calcaneum, and so supports its front border." Quainsays: "The lower internal corner projects backwards as a conical processbeneath the anterior extremity of that bone" i.e. os calcis.

Of these- descriptions, Macalister's is the most graphic. The process" undershoots" the os calcis, supporting it in a bracket-like way-in fact,in a very similar manner to that in which the plantar point, on thenavicular, supports the head of the astragalus.

FIG. 1. FIG. 2.

FIG. 3.

Fig. 1 shows the position of the calcaneal process in the chimpanzee. Fig. 2 shows an approxima-tion of the calcaneal process in man to its position in the chimpanzee. Fig. 3, absence of thecalcaneal process in man.

It is well developed in nearly all cases, and either nipple-like or spur-like in shape. It is sometimes very small, and occasionally absent(6 specimens). Amongst the Simiidw it is present in the chimpanzee andorang, but it is a rounded eminence situated near the middle of the margoplantaris posterior (fig. 1).

The shape of the whole facies articularis posterior, in these animals,presents an interesting contrast to the condition occurring in man. Thewhole surface dovetails with that of the os calcis, the cuboidal processbeing received into a well-marked depression. By this arrangement theos calcis and cuboid mutually support each other, much more than is thecase in man. The outer portion of the longitudinal arch of the foot, in

VOL. XLII. (THIRD SER. VOL. II1.)-JULY 1908. 28

Mr T. Manners-Smith

these anthropoids, is supported, therefore, by the interlocking articularsurfaces of the os calcis and cuboid.

Faces Articularis Anterior.

Outline of the Surface.-The surface in most cases (370-188 right, 182left) has the shape of a blunt wedge, the truncated apex of which isdirected outwards and backwards.

In 82 specimens it is somewhat quadrangular, with rounded angles.In 18 it approached the oval.

The Shape of the Articular Facets. -In some cases the whole surface isconcave from above downwards (dorsal to plantar surface). In most ofthese there is no, or only a slight, ridge separating the two facets formetatarsals 4 and 5. In some the concavity is confined to the surface

FIG. 4. FIG. 5.

Fig. 4, chimpanzee, showing concavity for 4th, shelving of surface for 5th metatarsal, andridge between the twyo facets. Fig. 5, man, showing the same arrangement.

for articulation with the 4th metatarsal. In one the concavity offacies articularis anterior is very irregular, and extends on to the faciesplantaris. A well-marked ridge may separate the two articulations. It isnot uncommon to get a shelving of the facet for the 5th metatarsal, outwardsand backwards. When these three characteristics are combined-i.e. aconcave surface for the 4th, a shelving of the surface for the 5th, and awell-marked ridge separating the two facets- we have the anthropoidtype of articulation in this situation (figs. 4 and 5). These conditions areall probably correlated with greater freedom of movement of the 4th and5th metatarsal bones, which is, in turn, dependent on the fact that the feetof the ancient Egyptians were not compressed artificially.

The surface is flat or convex in 114 specimens; more or less concave atsome part in 339. There is a ridge at the junction of the two facets forinetatarsalia 4 and 5 in 144 (61 right, 83 left) specimens. There is a slighttubercle at the junction of these facets, at the margo, plantaris anterioronly, in .112 specimens (54 right, 58 left), at the margo dorsalis anterior

400

Study of the Cuboid and Os Peroneum in the Primate Foot 401

in 55 specimens (34 right, 21 left), at both margins in 103 specimens(55 right, 48 left).

Another point to which Pfitzner has called attention is in connectionwith the facet for the 5th metatarsal bone. He has pointed out that thissurface may be subdivided by a very slight ridge into two; the outermostof these is for the tuberosity of the 5th metatarsal bone, and it encroaches

FsG. 6. FIG. 7. FIG. 8.

FIG. 9. FIG. 10.

These figures show the chief facet for external cuneiform. Fig. 6, almost equilateral triangle, orcupid's heart shape. Fig. 7, isosceles triangle. Fig. 8, kidney shape. Fig. 9, approachedthe oval. Fig. 10, oval.

to a slight extent upon the facies lateralis. I found this arrangement wellmarked in only 5 (3 right, 2 left) specimens, out of 422 examined (figs. 18 and19). In another specimen there was a well-marked facet on the facies lateralis,but there was no ridge separating it from the facies articularis anterior.It will be seen, therefore, that this subdivision is present only 'in a smallproportion of cases. This is to be expected in a non-boot-wearing people.On the other hand, when the feet are compressed artificially, there wouldbe a tendency for the tuberosity to be pressed against the cuboid.

Mr T. Manners-Sinith

Faces 2Medialis.Direction and Shape.-This surface looks upwards as well as inwards.

It is quadrilateral in outline, and offers for our notice (a) a facet or facetsfor articulation with the external cuneiform; (b) a frequent facet for thenavicular bone; (c) an occasional facet for the astragalus; (d) a rougharea for the attachment of ligaments.

(a) Shape of the articular facet for external cuneiform: rounded or"oval " (Cunningham); oval (Morris). In most cases this facet istriangular. To be more exact, in 106 (4858) cases it is an almostequilateral triangle. In 22 (14-8) cases it is an isosceles triangle withthe base at the facies dorsalis; in 76 (44-32) it is an isosceles trianglewith its base at the navicular facet. In 31 (12-19) it has the outline

FIG. 11. FIG. 12. FIG. 13.

Additional facet near anterior extremity for external cuneiform. Fig. 11, orang, second facet nearanterior end for external cuneiform. Fig. 12, man, shows similar facet to the above, which isoccasionally present. Fig. 13, man, shows the two facets for external cuneiform continuous.

of a cupid's heart. In 28 (18-10) cases it is distinctly kidney-shapedor crescent-shaped. In 50 (25 25) it approached the oval. It is acomplete oval in 17 (7-10). It is a half-oval in two specimens, both left.It is four-sided in 71 (30-41). It is pentagonal or mitre-shaped in 3 (2-1).

The additional occasional facet for the external cuneiform. Aninteresting difference between the human and the simian foot is theprojection of this surface forwards and inwards, in the former, near thefacies articularis anterior, which may encroach slightly on this projection.In the simian foot there is a second small facet for the external cuneiform(see fig. 11) on the site of this projection in man, and near the dorsalsurface of the bone. There are therefore two facets on the surface, inthese animals, for the external cuneiform, separated by a deep groove.The presence of this second facet in the simian foot is possibly due to the

402

Study of the Cuboid and Os Peroneum in the Primate Foot 403

manner in which the animal walks, i.e. the cuboid in these animalssupporting the navicular and cuneiforms.

This small second facet occurs in 20 (11 right, 9 left) specimens ofthe present series, or about 4 per cent. of those examined with referenceto this point. In some cases it is a quadrilateral facet with the posteriorangles rounded. Occasionally the two cuneiform facets are continuous(fig. 13).

(b) A frequent facet for the navicular. There was a facet for thenavicular in 215 specimens. In 121 cases the shape of this facet isfour-sided, and in most of them it has the posterior angles roundedoff. In some of the above it is almost square, in others rhomboidal,occasionally oblong; in 54 it is triangular or wedge-shaped, with the base

FIG. 14. FIG. 15.

Show the shape of the navicular facets. Fig. 14, quadrilateral. Fig. 15, triangular.

of the wedge directed anteriorly. In 32 it is semilunar or half-oval; in 8,pentagonal or mitre-shaped. Frequently the navicular facet extends tothe facies articularis posterior; in many cases, however, there is a roughdepression between them.

(c) In a few specimens there is a small facet for the astragalus situatednear the facies articularis posterior, and upon the facies medialis of thecalcaneal process. This was present in 3 specimens out of 537 examined.In 2 cases the facet was semilunar, in the other almost oval, in outline.

(d) The rough area for the attachment of ligaments. With the ex-ception of the above facets, the whole of the remaining portion is roughfor the attachment of ligaments. There is a depression between the cunei-form facet and the facies plantaris in 458 specimens. In 194 of thesethere is a small tubercle immediately behind the depression.

The extent of the rough area behind the cuneiform facet will of coursedepend upon the absence or presence of a navicular articulation.

Mr T. Manners-Smith

Faces Lateralis.This surface is the least extensive of all. It is occupied chiefly by

the commencement of the groove for the peroneus longus tendon, and bya portion of the peroneal sesamoid facet. Since both of these are situatedchiefly on the next surface, they will be considered with it.

F~IG. 16. FiG.. 17.

FIG. 18. FIG. 19.

Figs. 16 and 17, astragalar facets. Figs. 18 and 19, facets for the tuberosity of the 5th metatarsal bone.

Attention has already been drawn to the fact that the tuberosity of the5th metatarsal hone may articulate with this surface (figs. 18 and 19).

Facies Plantaris.

This surface offers for our notice (a) the groove for the peroneuslongus tendon; (b) the ridge bounding the groove posteriorly; (c) thefacet for the sesamoid bone or cartilage in the tendon; (d) the calcanealtubercle projecting from the posterior and inner corner of the surface; (e)a triangular area posterior to the ridge, between it and the facies posterior.

404

Study of the Cuboid and Os Peroneuni in the Primate Foot 405

(a) The groove for the peroneus longus is well developed (deep) in80 (46 34) specimens. It is moderately well developed (fairly deep) in182 (93389) specimens. It is slightly developed in 197 (90 107) specimens;almost absent in 32 (12 20), totally absent in 12 (7 5).

(b) The ridge bounding the peroneal groove. There is as a rule, ofcourse, a direct relationship between the development of the ridge andthe depth of the groove: thus, in most cases, as one would expect, a deepgroove is bounded posteriorly by a well-inarked ridge. Ini many cases,however, the ridge is well developed when the groove is quite shallow.In some specimens the ridge is narrow and fairly sharp, in others it isrounded. The most interesting point in connection with it is thepresence of the facet for the sesamoid element in the tendon of theperoneus longus.

(c) The sesaimoid facet. This is situated chiefly on the facies plantaris,though it may encroach on the facies lateralis. Sometimes it is situatedin the peroneal groove itself rather than on the ridge. It is generallyconvex or flattened, occasionally concave. It is oval or nearly oval inoutline in most cases, but in some of these it has a process extendingalong the peroneal ridge forwards and inwards; this gives the wholefacet a bottle-shaped appearance.

A process, too, generally quadrilateral in outline, may extend into theperoneal groove. This gives the whole facet a somewhat mushroomn-likeappearance.

Both the above processes may be present.In other specimens the facet is half-oval, triangular, wedge-shaped, or

rhomboidal. Sometimes it is supported by a small bony process, whichjuts out posteriorly and plantarwards and supports the calcaneal articula-tion on its outer side.

The proximity of the peroneal facet to the calcaneal articulation. Inmany cases the calcaneal facet extends right up to the calcaneal articula-tion; ill others there may be a grooved interval between the two. Of286 specimens examined with reference to this proximity, in 123 (66 right57 left) the peroneal facet reached the calcaneal. In 163 there was aninterval between the two, usually narrow and grooved, occasionally wideand shallow. The proximity of the two facets will be referred to againunder peroneal sesamoid.

(d) The tubercle supporting the calcaneal process or spine. rhis waspresent in some form in most cases. It was well developed in 129 (68X61)specimens. In most of these the calcaneal process was well developedalso. In some, however, the spine is well developed when the tubercleis small. It is interesting to notice that both the calcaneal spine and the

Mr T. Manners-Smith

supporting tubercle are absent in the Simiidae. In these animals, in placeof the spine is a rounded eminence, confined to the facies posterior andreceived into a depression in the os calcis. In none of the specimens wasthere any indication of the separate existence of this tubercle.

FIG. 20. Fia. 21.

FIG. 22. FIG. 23.

Show facets for os peroneum. Fig. 20, oval in outline. Fig. 21, nearly oval. Fig. 22,flask-shaped. Fig. 23, process extending from facet into the peroneal groove.

(e) The area behind the peroneal ridge, between it and the faciesposterior, is generally smooth and perforated by foramina for nutrientvessels. In most bones it is depressed, in some markedly so, therebeing in these a deep concavity between a well-marked peroneal ridge anda prominent calcaneal tubercle. This is for the short plantar ligament.There is a well-marked depression in this position also in the Simiidwe,though in these animals the calcaneal tubercle is absent.

406

Study of tihe Cuboid and Os Peroneiein in the Primate Foot 407

IFce(W Dorsalis.

This surface is four-sided. It is prolonged upwards and inwards at thesuperior internal angle, where it not infrequently has a small tuberclefor the attachment of the internal calcaneo cuboid ligament.

This surface is often somnewhat smooth, and is perforated by foraminafor nutrient vessels.

There is an eminence or ridge with a groove behind it near the outerpart of the margo dorsalis posterior in many cases.

There is an eminence or oblique ridge running forwards and inwardsjust ine front of the position of the last-mentioned ridge in others.

There is a slight groove with sometimes a ridge behind it near themargo dorsalis anterior in manly specimens. Sometimes the hlone is concaveabout the centre.

THE OS CUBOIDES IN THE ANTHROPOI1 APES.

ANTHROPOIDEA. SIMIDJE.ANTIHROPOPITIECUS TROGLOD YTES.

Fancies Posterior.This surface is somewhat wedge-shaped, with the base of the wedge

directed upwards and outwards. It is concavo-convex from above down-\ards (in its long diameter). It possesses a small calcaneal process which,however, is not spine-like, but rounded, and fits into a depression on thefacies articularis anterior of the os calcis. This eminence, together witha coneavity immediately below it, makes the whole facies posterior dovetailwith the fucies anterior of the os calcis. This is probably correlated withthe greater inversion of the foot in these animals, and as a result of thisinterlocking the posterior surface of the cuboid not only articulates with,but is supported by, the os calcis; in man, on the other hand, it is ratherthe cuboid which supports the os calcis by means of its calcaneal process.

The above process seems to act as a pivot on which the cuboid turns,when the lateral movements are performed at the transverse tarsal joint.

Fa(cies Anterio)r.The whole surface is wedge-shaped, with its base directed supero-

externally. It is subdivided by a slight ridge or eminence into twoarticulations for the 4th and 5th metatarsal bones. These are quitedifferent in character.

A dticula(tio Clao- flt(1(ctas Ik.-This is (1uadrilateral in outline, is

4Mr T. Mianners-Snmith

distinctly concave both from above downwards and from side to side. Itarticulates with the rounded inferior portion (outer portion it would be inhuman anatomy) of the 4th metatarsal bone. There is a small tubercleon the margo superior close to the superior anterior angle of this surface.

A rtic alat o ctbo-mnc/dt(mt Si V.-This is wedged-shaped, with the baseof the wedge at the ridge separating this surface from articulatio cubo-mnetatarsi IV. There is a slight tubercle, at the dorsal extremity of thisridge, which fits into the interval between the 4th and 5th metatarsals. Thesurface for the 5th metatarsal bone is flattened or slightly convex, andshelves towards the plantar surface.

The Fa(cies illedictlis..The facies medialis presents two facets-a large posterior one, which is

oblong, with the angles rounded off, or somewhat semilunar or wedge-shaped, with its base at the imiargo posterior. This surface is for articula-tion with both the navicular and the external cuneiform. The facet forarticulation with these two bones is practically one, only a very faint ridgemarking the separation. The second facet is very small and somewhatwedge-shaped in outline, with its base directed anteriorly. It is also forarticulation with the external cuneiform. There is a rough depressed areabetween these two facets for the attachment of ligaments.

Facies Lateralis.

From the position of the foot in these animals, it looks downwardsrather than outwards. It is marked by the commencement of the groovefor the peroneus longus.

Faces Plcata ris.

This surface possesses a ridge, with a peroneal groove in front of it,and a rough surface behind it.

The ridge is sharper than inl human anatomy, and is not marked by aperoneal facet, though this is present in the fresh state. The peronealgroove is deeper and narrower than in hIiuma anatomy. The roughligoamentous surface behind the ridge is somewhat depressed and is markedby one or two large umedullary foramina.

F(icie8s Domrsalis.The surface is quadrilateral in outline. There is no groove near its

margo dorsalis posteriorl.

408

Study of the Cuboid and Os Peroneuin in the Primate Foot 409

SIMIA SA TYR US.

Faces Posterior.

This surface is somewhat senilunar or wedge-shaped in outline. It isconicavo-convex from above downwards. It has a calcaneal process similarto that in the chimpanzee.

Facies Antterior.This surface forms a more blunt wedge than in the chimpanzee, and

the two facets into which it is divided are usually separated by a more pro-niinent ridge than in that animal. There is a little tubercle in three ofthe specimens at the plantar end of the ridge, and one at each end in afourth specimen.

Airtlcul(ttio catbo-ni-etatarsi IV.-The facet is quadrilateral and concaveas in the chimpanzee.

Articdathio cubo-net(tdarsi V.-This has the shape of a blunt wedge,and shelves considerably towards its apex, so that the surface looksdownwards and outwards as well as forwards.

Fac ies Mledialis.This possesses, in three specimens, two wedge-shaped facets-a larger,

posterior, with its base directed backwards, and a smaller, anterior, withits base directed forwards. The posterior facet articulates with both thenavicular and external cuneiform, the anterior with the external cuneiform.Between the two facets is a rough surface for interosseous ligaments.

Faciees Lateraltis.This is marked by the comninencemnent of the groove for the peroneous

longus tendon.Facies Plan tarnis.

This surface presents the well-marked ridge bounding the peronealgroove posteriorly.

The ridge, however, is not marked by a facet for a peroneal sesamoidbone, and is sharper than in human anatomy. The peroneal groove isdeeper than the corresponding groove in man. There is the rough surfacebehind the ridge, which is marked by medullary foramina as in thechimpanzee.

Faces Dorvsalis.rphele is a very slight narrow groove near the mnargo dorsalis posterior

iil two of the specimens.

Al r T. Manners-Sm-nith

HYLOBA TES.

Faciees Poster io} .

Surface somewhat wedge-shaped, mnuch flatter than in chimpanzee andorang. The cuboidal process is very small, and this bone and the os calcisdo not dovetail as in the other anthropoid specimens.

Faces Anuterior.Artic alatio c b)o-muet(ala.isi IV.-A small quadrilateral concave facet

for the rounded proximal extremity of the 4th metatarsal bone.2Xtote.- Tliis is the only one of the metatarsal bones which possesses a

rounded extremity at its base. A rticatlatio cabo-ntetatarst V. iswedge-slhaped, and shelves backwards towards the inferior aspect ofthe bone.

Fadces Laute raeis..Groove for peroneus longus.

F(acies Plaittaris.Groove for peroneus longus with ridge behind it. No facet on ridge

for sesamoid bone.Faccies Dorsalis.

Nothing of interest in connection with this surface.

THE PERONEUM OR PERONEAL SESAMOID

The account of this structure is chiefly of a comparative rather thanof a descriptive nature. Trhe description of this element has been soexhaustively dealt with by Professor Ptitzner that little remains to beadded. He found it present in 8 to 9 per cent. only.

Positioht. In most cases the facet on the cuboid for the peroneum,as stated earlier, is situated chiefly on the facies plantaris. Its varietiesof shape have been considered in the description of the cuboid. Withreference to the position of the facet, Pfitzner states: " Only in extremecases does the peroneum extend up to the calcaneo-cuboid articulation oreven beyond. Usually it remains far removed froni it. If, then, directrelationships have existed formerly between calcaneus and peroneum,these have, in any case, first retrogressed." In the series of Egyptiancuboids which I examined xvith reference to this point, in 43 per cent.the peroneal facet reached the calcaneal in the remainder there was aninterval between the two facets.

410

Study of the Cuboid and Os Peroneum in the Primate Foot 411

The proximity of the peroneal facet to the calcaneo-cuboid articulation,in man, is interesting, since these two facets are nearer each other in thelower primates than in man. Indeed, in the specimens of Cynocephaluswhich I examined, the peroneum articulated not only with the cuboid, butto a slight extent with the anterior and outer extremity of the os calcis.

The Surfaces of Contact.-According to Pfitzner, the contiguous surfacesof the peroneum and cuboid are, in man, not truly articular. He states thatthey do not possess two hyaline clad articular surfaces in direct contact, butthat, even when cartilage is present, it is always covered by a layer ofconnective tissue. This condition he regards as a sign of retrogression.In the lower apes, according to Gillette and Pfitzner, the bones articulateby means of a hyaline cartilaginous surface. In the specimens which Iexamined microscopically, I found much more fibrous tissue in man thanin the lower primates.

THE PERONEUM IN OTHER PRIMATES.

SIMIIDRE.

GORILLA. ANTIHROPOPITHECUS TROGLODYTES. SIMIA SA TYRUS.

There is merely a slight thickening in the peroneus longus tendon,no peroneum. There is a cartilage-covered surface on the cuboid, forarticulation with the above thickening in peroneus longus. This articularsurface is confined to the cuboid; it is not found in the dry specimens oforang and chimpanzee which I examined.

HIYLOBA TES.

There is a sesamoid, which is small and bony, in the tendon of theperoneus longus. The facet on the cuboid is confined to that bone, andthe peroneum does not articulate with the os calcis.

CERCOPITHECIDAE.CYNOCEPIAL US.

Peroneum is cartilaginous. The cartilage articulates, to a slight extent,with the fore part of the os calcis.

CERCOPITHECUS FULIGINOSUS.

Peroneum of fair size, cartilaginous, somewhat oval. The facet on thecuboid is cartilage-covered and confined to the cuboid.

4Mr T. Manners-Smith

CERCOPITHEOUS CALLIT-RICHUS.

The peroneum is well developed, ossified, and oval in shape. The faceton the cuboid is oval in shape, cartilage-covered, and confined to the cuboid.The peroneum is not in the centre of the tendon, for it has more fibrousstructure superficial to it than on its articular surface.

In three.other specimens of Cerco) ithec8s the peroneum was somewhatoval in shape; in two, cartilaginous; in one, osseous.

In none of these did the peroneum articulate with the os calcis, thoughin all, the peroneal facet on the cuboid extended as far back as the calcaneo-cuboid articulation.

MACA CUS NEMESTRINUS.

In both of these specimens examined, peroneum was fairly welldeveloped, osseous, and oval in shape. The cuboid facet is oval andcartilage-covered. The peroneum does not articulate with the os calcis,though in one of them the peroneal facet is close to calcaneo-cuboidarticulation.

AIACACUS RHESUS.

Peroneum is very small, chiefly cartilaginous; osseous towards thecentre to a slight extent.

SEMANOPITHECUS.

In this specimen peroneum is fairly well developed, oval in shape, andbony. Facet on the cuboid is oval, cartilage-covered, and confined tothe cuboid.

CEBIDME.

In Cebas the peroneum is small, oval, and cartilaginous. Facet is confinedto the cuboid.

In Lagothrix slight thickening in the peroneus tendon: cuboid facet isnear the calcaneo-cuboid articulation.

In Ateles merely a thickening in peroneus: facet on cuboid is close tocalcaneo cuboid articulation.

In Chrysothri- the peroneum is small and cartilaginous. The facet onthe cuboid is confined to that bone.

HAPALIDE.

HAPALE.

Two specimens examined. In both these specimens the sesanmoidbones were absent; no trace, cartilaginous or otherwise.

412

Study of the Cuboid and Os Peroneum in the Primate Foot 413

LEMIUROIDE.LEKLURID.

Merely thickening in peroneus. Facet on cuboid is cartilage-coveredand confined to the cuboid, though it extends as far backwards as calcaneo-cuboid articulation.

SUMI.MARY OF THE MOST INTERESTING OBSERVATIONS.

(1) The shape of the facies articularis posterior in the Simiidve, andthe dovetailing of the cuboid and calcaneuni in these animals.

(2) On the facies articularis anterior, a combination in some cases ofthe following anthropoid characteristics:-

(a) A concave surface for the 4th metatarsal.(b) A shelving of the surface for the 5th metatarsal downwards

and outwards.(c) A well-marked ridge separating the two articulations.

(3) The frequent presence of the articulatio cubo-navicularis.(4) An occasional facet for the astragalus.(5) A second facet for the external cuneiform situated at the anterior

end of the facies medialis.(6) The constant presence of the last-mentioned facet in the Siniidoe.(7) An occasional facet on the facies lateralis for articulation with the

tuberosity of the 5th metatarsal bone.(8) The degree of proximity of the peroneal facet to the calcaneo-cuboid

articulation, in man and in other primates.(9) The articulation, in the Cynocephali, of the peroneum with the

anterior and outer extremity of the os calcis, as well as with the cuboid.(10) The more constant occurrence of the peroneum amongst the

lower than amongst the higher primates, especially in the Old Worldmonkeys below the Simiidw.

(11) The great variability in shape of the facet for the os peroneum.(12) The large amount of fibrous tissue in the cartilage of the peroneal

facet in the human subject.(13) The frequent presence, in man, of a small slip fromt the peroneal

sesamoid to the base of the 5th metatarsal bone.(14) rrhe fact that in none of the specimens was there the slightest

evidence of a cuboides bipartitum.(15) The fact that in none of the specimens was there the slightest

evidence of the separate existence of Pfitzner's so - called cuboidessecundarium.

414 Study of the Cuboid and Os Peroneum in the Primate Foot

In conclusion, comparing this bone with the navicular, the greatsimilarity in general outline of the specimens of cuboid to each otheroffers a strong contrast to the great variability in the shape of thenavicular. This is partly due to mechanical conditions on the two sidesof the foot, and partly to the different times at which the bones ossify.

Though the two bones are miarkedly alike in each possessing a so-calledsesamoid element in its neighbourhood, the behaviour of these elenients isdifferent on the two sides. On the inner aspect of the foot, the tibialsesamoid (tibiale externum-i) may either articulate or fuse with the navicular,in the latter case, prolonging the tuberosity proximally. On the outer side,though the peroneal sesainoid (os peroneuin) articulates and does not fusewith the cuboid, the large amount of fibrous tissue in the joint probablyindicates that the articulation is regressing in man; in other words, that thecondition is a step on the way either to disappearance or to fusion of theperoneal element with the cuboid. The os hamuli proprium in the carpushas possibly passed through the samine transition. The explanation of thesedifferences, both in the hand and foot, mtay depend upon the fact that allthese elements are probably the remains of additional digits, which mayapparently assume sesamnoid functions only, as the os pisiformie, or osperoneum, fuse entirely like the os hamuli proprium, or, as in the case ofthe tibiale externum, play either of these parts.

BIBLIOGRAPHY.

PFITZNER, " Beitrage zur Kennttiiss des menschlichen Extremititteniskelets,"Morphologische Arbeiten, hrsg. von G. Schwalbe, Pd. vi., 1896, S. 245.