Materials for the Study of Variation Treated with Especial Regard to Discontinuity in the Origin of Species

[The case described by GBANDIN, Amer. Jour, of Obstetrics, IMS?, xx. p. 425, fiy., is probably a case of a pair of limbs composing a Secondary Symmetry attached to and deforming the limb belonging to the Primary Symmetry and convsi'unding with that uf the other side. The nature of this case will be better understood when evidence as to the manner of constitution of Secondary Symmetries has been given.] *504. Macacus sp. A monkey, full-grown, having nine toes on the left foot; right foot normal, upper extremities not preserved. The specimen is described as No. 307 in the Catalogue of the Temtofn>/ical Series (1872) in the Mus. Coll. Surg. (Huuterian specimen). Though I am disposed to agree in the main with the view of the nature of the specimen given in the Catalogue it is not in my judgment possible to decide confidently in favour of this view to the exclusion of all others. For this reason the specimen is here described afresh. This is the iinnv necessary as the account of the Catalogue is incorrect in some particulars.

Extra parts are present in the limb and in the pelvic girdle. (Figs. 97 and 98.) The names to be given to the parts depend on the hypothesis of their nature which maybe preferred. In general terms it may be stated that the ventral or pubic border of the girdle and the internal ( t ibial) border of the limb are nearly normal. The external (fibular) border of the limb is also normal, but between these there are in addition to the normal parts other structure-, whose true nature is somewhat uncertain.

The apj tcaraiices may be realized best in the following way. Suppose that two similar left feet lie in succession to each other, the " posterior " having its hallux next to the minimus of the "anterior," so thai the digits read I, II, III, IV, V, I, II, III, IV, V. Now if the two feet could interpenetrate so far that the minimus of the " anterior " foot took the place of the hallux of the " posterior," this second hallux not being re presented, the condition of this specimen would be nearly produced. In the same way the left pelvic girdle is just what it would be if two left innominate bones were placed in succession, the ischium of the " anterior " superseding the pubis of the posterior. As in the foot, so in the innominate, of the portions which coincide the parts belonging to the anterior are alone represented. Something very like this was seen in the case, for instance, of the imperfect division of vertebrae in Python, No. 7.

The chief difficulty attending this view of the nature of the case is the fact that as regards the tarsus the " anterior " foot /ji, head by which femur articulates. h", supernumerary head (?). gt, great trochanter. gt2, " posterior " great trochanter. It, lesser trochanter. t, tibia, fib1, " anterior fibula." fib-, "posterior" fibula (?). clc, calcaneum. As, astragalus, nav, navicular. ?iar2, supposed second navicular. c1 — c6, six cuneiform bones, c3, the ecto-cuneiform of " anterior " foot, cb, cuboid.

lacks the external (filmlan partof a tarsus, viz. the cuboid and cal'-aiiemn. There is a cuboid, cb, and a calcaneum, c, for the " po>terinr " funt. lint none finthe "anterior." The bone c3 might of roiir-e In- calli-d a cuboid: but if this is a cuboid there is n<> ecto-cuneiform fnr the anterior foot. The account given in the Cutulnrfiie avoids these difficulties by the statement that each foot hathree cuneiforms and a cuboid, declaring that there isasecond cuboid between the t\v.. sets of cuneiforms. This is nevertheless incorrect, for tinwhole distal series in the tarsus contains only seven bono and not eight. The mistake has no doubt arisen by (•minting r:i i \\jce over. The Catalogue is also in error in neglecting the fact that tintarsal articulation of the digit 2 is quite abnormal. Similarly in tincms, there is no good reason to affirm that the lionr jiltis a fibula lather than a tibia. The Catalogue regards it as a sec,, nd tibia, but I incline to speak of it as the fibula of the 'anterior' foot following the view already indicated. As I have said, the leg is almost normal in the structure of its external border and almost normal in its posterior border, but between these the nature of the parts is problematical. All that can be done is to describe the parts as they are seen.

Beginning at the external (fibulur) border of the foot there is a nearly normal series of three digits, 9, 8, 7, fashioned as V, IV and III I'i'.. '.'•>. I. Innominate bone of Macacus, No. 504. i1, p, is1, tl, of1, ilium, pubis, ischium, ischial tuberosity and obturator i'oranien of the supposed anterior of tli^ -mil.'; tinji.-irts marked 2 being the corresponding structures of the supposed posterior pm t. II. Details of tarsus of the same. Digits numbered 1—9 from the inside, c, caloaneum. »'. navicular of "anterior" foot. «-, navicular of "posterior" foot, cb, cuboid, c1— r6, six bones placed as cuneiforms.

respectively, the Y and the IV articulating with the cuboid (<:/,) ,-md the III with an external cuneiform, c8, as usual. There is a middle cuneiform, c5, bearing a digit, 6, which is almost exactly formed as a II. Internal to this point the parts can only be named with hesitation. The tarsal bone, c4, of the distal series internal to c5 is shaped like another c5, but the digit which it bears rather resembles a minimus. This is succeeded by a tarsal bone, c3, shaped like the external cuneiform, c6, but it bears a digit of the length suited to an annularis. Internal to this are two tarsal bones of the distal row, c2 and c1, which bear three digits, 1, 2, and 3. Of these the most internal is undoubtedly an internal cuneiform ; it bears firstly a slender but otherwise normal hallux with two phalanges, and secondly, it contributes (abnormally for an internal cuneiform) to the articulation of a digit, 2, which is thinner than all the others and resembles rather a minimus than an index. The digit, 2, also articulates with c2 which chiefly supports the third digit.

Between the metatarsals of the digits 5 and 6 there is a considerable space, owing to the fact that the head of the metatarsal of 6 is prolonged upwards like that of a normal metatarsal V. In addition to those described are four other tarsal bones : firstly, a calcaneum c, which is rather smaller than that of the normal right leg. It articulates with the cuboid, cb, with the astragalus, A, and with the bone, n2. The astragalus is very large in its transverse dimension but its length is less than that of the normal astragalus. Peripherally it bears two bones, firstly, a navicular, n1, and secondly, a bone of uncertain homology, marked n2 in Fig. 96. The navicular articulates with c1, c2 and c3, together with the bone n2. The latter, n2, articulates with c3, c4, c5, c8, and also with the cuboid, cb, the astragalus and calcaneum and navicular. From its form and relations it is probably a second navicular.

The bones of the crus are three. Firstly, a tibia, tib., which is rather thinner than the normal bone and is somewhat bowed inwards. Passing as a chord to the curve of the tibia there is a thin bone, Jib1, which is tendinous in its upper part. External to this, articulating with the external condyle of the femur there is a third bone, Jib2, which has nearly the form and proportions of a normal fibula. All three bones articulate with the large astragalus.

The femur is about half as thick again as that of the right leg. Its head is nearly normal in form, articulating with the rather shallow acetabulum. The lesser trochanter and the internal border of the femur are nearly normal. Anteriorly and externally there are the following parts. Upon the external border there is a projecting callosity, clearly being a great trochanter in its nature. Internal to this there is a knobshaped, rounded protuberance, which in texture so closely resembles the head of a femur that it is almost certainly of this nature. It is rounded and smooth as though for articulation with an acetabulum, though it stands freely. Between this tuberosity and the real head of the femur there is a third tuberosity, apparently representing the end of the great trochanter of that limb which has been spoken of as "anterior." The peripheral end of the femur is nearly normal on its inner side, while on the outside it is considerably enlarged. The ex

ternal condyle is thus much larger than that of the normal femur, but there is in it only a very -liirht su.L'icestion of a division into two parts. The innominate bone haan ilium which anteriorly is normal, but which po>teriorl\- enlarge- and t<> >ome extent divides into two parts, i' and i2. < »t' tlie.se the ventral part. 2'', unites with a nearly normal pubis, />, and bounds the shallow acetabulum with which the femur articu- Lates. The rest of this aceialndum is made up by the ischium, in*, of the ''anterior" limb, which together with the pubis bounds an obturator foramen, of1. Dorsal to these parts the ilium has a partly separated portion, r, which forms part of the wall of a cavity apparently representing the acetabulum of the "posterior" limb. Dorsal to this a complete ischium arises which bears a normal ischial tuberosity and curves round a second smaller obturator foramen, of".

In so far as the foregoing description involves conceptions of homology it is merely suggestive, but the structure of the innomi- n. -i t e bone leaves little doubt that the nature of the parts is much as h> iv described. Nevertheless the appearance of the digits 5 and (i ami of the tarsal bones c3 to c6 somewhat suggests that there is a symmetry about an axis passing between the digits 5 and 6 : but it' .'• were a minimus and if 6 were fashioned as an index, which it is, the appearance of a relation of images would to some extent exist in any case. This appearance is however confined to the dorsal aspect of the foot and is not present on the plantar aspect.

This case, if the view of it proposed be true, differs from other examples of double-hand (e.g. Nos. 491 to 499) in that the Repetition is Successive and is not a Repetition of images ; for the digits stand I, II, III, IV, V, II, III, IV, V, and not V, IV, 111,11, [I], II, III, IV, V as in those other cases. In this respect it is so far as I know unique. Those who have treated the subject of double-hand generally make reference to the following records. ECEFF, 1>, conceptu, Frankfurt, 1587, PI. 41; ALDRO- VAXDI. Mmixtr. Hi.it., 1CJ-J. p. 495; KEBCKRING, lib*, tinat., Amst. 1670, Ob*, xx. /'/., but tin1 descriptions are scarcely such as to be useful for our purpose. A case quoted by DWICIIT, Mmt. I lout. Soc.qf X. II.. iv. No. x. p 474, from i>u CAUROI, Jour. det Scavaiu, lf'>',tr>, pub. 1697, p. 81 [originally quoted by MOR.VND and misquoted by many subsequent authors], is probably not an example of double-hand (see No. 522).

Cases of Polydactylism in Man and Apes not associated with definite change of Symmetry. the evidence as to polydactylism in general the foregoing cases have been taken out and placed in association as exhibiting the development of a new system of Symmetry in the limb. It will have been noticed that in all of them the external (ulnar or tibular) (.arts of the limb remain unchanged, and the parts not represented in the normal are on the internal (radial or tibial) sides. In the remaining cases of polydactylism, which constitute tli-1 ^re.-it majority, there is no manifest change in the general symmetry "f the limb.

These general phenomena of polydactylism have been observed from the earliest times and the literature relating to the subject is of great extent. Most cases known up to 1869 [not including STRUTHERS' cases] were collected by FORT, Difformites des Doigts, Paris, 1869, and independently by GRUBER, Bull. Ac. Sci. Pet., xv. 1871, p. 352 and p. 460, and good collections of references have subsequently been published, especially by FACKENHEIM, Jen. Zeits., xxii. p. 343. Of the whole number of cases the majority fall into a few types, and a great part of the evidence may thus be easily summarized and illustrated by specimen-cases. The forms of polydactylism thus constantly recurring may be dealt with conveniently under the following heads.

(2) Duplication of single digits, especially of the pollex and Besides these are a certain number of cases not included in the above descriptions, and of them an account will be given under the heading As bearing upon the frequency of the several forms of polydactylism it may be stated that in this irregular group are included all cases which I have met with that exhibit any feature of importance in departure from the cases otherwise cited. For the purpose of this list I have examined every record of polydactylism to which access could be obtained.

(1) A. SINGLE EXTRA DIGIT EXTERNAL TO MINIMUS IN HAND OR FOOT. This is one of the commonest forms of extra digit. In the great majority of such cases the extra digit is not complete from the carpus or tarsus but arises from the nietacarpal or metatarsal, less often from one of the phalanges, of the minimus. The attachment may be either by a direct articulation upon the side of one of these bones, or they may give off a branch bearing the extra digit. In a not uncommon form of the variation the extra digit has no bony attachment to the hand, but is a rudimentary structure hanging from some part of the minimus by a peduncle. Of these several forms the following are illustrative cases.

In tinfor. r<>iiiK cases the extra digit articulates immediately with the side or hcail of nictaraipal or metatarsal, but sometimes in the manus and often in the pes tin- .li^it aitinilatt - at the end of a branch given off by the metacarpus (MOUANI>, iliiil., lii.'. 3, and numerous other records), or by the metatarsus (MoiiAXD, I. c. ; Hylobates leuciscus (Fig. 99) having an extra digit in the left manus articulating externally with the metacarpus V and in the right manus articulating with a branch from it. Mus. Coll. Surg., Teratol. Ser., No. 307, A.

I'l ,. '.i'.t. Iliiluliitt,'* l<'in-i.-irit.<. No. ."Os, minimus of right and left manus bearing ;i -upernumerary digit articulating with the metacarpals. Kxtra digits u\t' i nal to the minimus are occasionally complete, in^:i iii''t:ii"ir|iul i>r niftalai'sal and three phalanges, standing truly in aeries with the other (limits, but to judge from the records this riiinplrtr furiu i^ d«'ridcdly i-aiv. In the tii-st of the fbllowing f\;inipli's -ivrii it should be noted that the digit standing fifth,

that is to say, as minimus, was itself rather longer than it should be in the normal, thus illustrating the principle with regard to the Variation of a small terminal member of a Meristic Series on becoming penultimate which was predicated especially in regard to Teeth (see p. 272). In MORAND'S case the interesting fact of the partial assumption by the sixth digit of anatomical charact'T- proper to the minimus is commended to the attention of iln reader.

*509. Girl : one extra digit on the external side of each hand. The normal little fingers are rather longer than usual and the extra fingers have nearly the same length. Each has three phalanges. Neither of the extra fingers can be moved separately from the finger adjacent to it. In the left hand the extra finger is borne on a supernumerary met a- carpal which lies parallel with the normal metacarpal V. Each extra digit can be opposed to the pollex. In the right hand the extra finger is borne on the enlarged head of the fifth metacarpal. BERANGER, Bull. Soc. d'Anthrop., Paris, 1887, Ser. 3, x. p. 600.

*510 Man (parents normal, one brother had six digits on each extremity, six other members of family normal) having an extra digit external to minimus on both hands (Fig. 100) and both feet, in series with the normal digits. Left hand : unciforni abnormally large, having two articular facets, one for the metacarpal of the fifth and the other for that of the sixth digit. The sixth metacarpal bears a digit of three phalanges of which the second and third were very short. [It does not appear that V was of increased length.] Right hand : metacarpals normal in number, but the fifth is very thick, having in its peripheral third 011 the external

FIG. 100. Palmar views of the bones of the hands of No. 510. (After OTTO and surface an articulation for a short digit of three phalanges, the second and third bein^ \<-ry -mall. Feet : well formed ; cuboid of size greater rh.ui tinnormal. hearin'_r the proximal end of two united fifth and sixth metatarsals. Karl, >.f these is separate peripherally and bears a digit [of •"• phalanges to judge from the figure (tig. Cj] in series with the normal toe-, hut shorter than the minimus.

.!///>.•/->. In tin- I ft hand the sixth digit was fully supplied with niu-eles. There were two extra interossei and the extensor communis sent tendons to the sixth digit. The abductor, the flexor brevis and the flexor ossis metacarpi which in the normal are proper to the minimus were all inserted into the sixth digit instead. In the r'fjlit li'ni'1 the extensor communis gave a tendon to the sixth, whieh also p. messed a proper abductor, but the fifth had no special extensor. Of the flexors the sublimis gave a tendon to each of the digit> index, medius and annularis, none to the fifth, but a small slip to the .sixth. The flexor profundus gave four tendons as usual, but from that going to the fifth a small tendon passes off laterally and piercing the sublimis is inserted as usual.

In both feet the muscles were similar. The extensor longus gave a tendon to the sixth digit, and the extensor brevis does not. The flexor longus has four tendons as usual, none going to the sixth digit ; the tlexor brevis has four normal tendons and an extra one for the sixth. The two tendons proper to the fifth (minimus) go to the sixth. The interossei are normal and there are only two lumbricales, one for the second digit and one for the fourth. MORAXD', Mem. de I' A cad. Jioy.

the muscles in regard to the fifth and sixth digits in this case is worthy of special attention. If the morphologist will here propose to himself the question which is the extra digit, he will find it unanswerable. In the riirht hand, judging from the bones, it may seem evident that the fifth with its complete metacarpal is the minimus and that the sixth is i new structure ; but the condition of the feet and the right hand taken with that of the left, make a series or progression from which the

similarity of the variation in each of the three states is evident; hence, it' it is thought that the most external digit in the right hand is the extra part, it must also be held that the external or sixth digit in the left hand is the extra digit. But this digit in respect of its muscles has some of the points of structure peculiar to a minimus, while the fifth digit or supposed miniums on the contrary is without these characters. llent-e neither digit is t/n' minimus. Just as in the Condition III (see

p. ."'!'<') of the hand, we saw that on the presence of a digit internal to the. pollex, the pollex itself may be promoted to be a finger-like digit with three phalanges, so may the fifth digit be partially fashioned as a more 1 The similar description- ;m<l film's <_'i\vn by OTTO, I.e., PI. xxv. figs. 9 — 11, Sri ]-.]<:, l'l>. mifirli. I Ynr, /<•;,.--. </. I''in:i,-r u. /<•/„ >/, AMMON. !>/,• ,;/<,/,•/>. AY. d. Jlenxi-h., all refer, I believe, to this one original case of Moraiid's. though the fact is not -tat-'d and though several authors (liurm.i;. ^-c.) quote them as separate cases. Seerig states that his iL'mvs arc ('nun preparations in the Breslau Museum. These figures a'.'rre exactly with those of Otto, which again agree closely with those of Moraiid but give more detail as to the carpi, taken no doubt from the actual -p. riinens which had been acquired by the Breslau collection. I have therefore Otto's figures, though taking the important descriptions from Moraud.

central digit on the presence of a digit external to it. If therefore it be still called the "minimus" this term can only be applied to it by virtue of its ordinal position. ] Apart from cases of extra digit external to the minimus, cases of duplication of the pollex or hallux (to be considered below), and cases of extra digits internal to the pollex or hallux associated with change of symmetry of the digital series, the remaining cases of single extra digit are very few. In other words, it is with digitsas with Meristic series in general, when a new member is added, the addition taking place in such a way that homologies may be recognized, it is most often at one of the ends of the series that the addition is made. Cases of extra digits in other positions are in Man and Apes very rare, and even in some of the few recorded cases of a new digit arising on the inner side of the minimus (No. 511) it should be remembered that this inner digit is judged to be the extra one rather than the outer mainly by reason of its smaller size. I can only give particulars of few such cases, and of the remainder no details are available.

*511. Simla satyrus (Orang-utan), having a rudimentary extra digit arising from the internal side of the minimus of each hand : feet normal. In the left rnanus the minimus has all joints nioveable as usual; the first phalanx is normal, but the second is bent outwards nearly at right angles, thus making room for an extra digit arising from the first phalanx and directed inwards. This digit is fixed and has no articulation and no nail, but it is in its outer part bent back again towards the minimus with which it is webbed. The structure in the right manus is almost the same but the extra digit is larger and in its outer part free from the minimus, bearing a nail. BOLAU, Verli. natiirw. Ver. Hamburg, 1879, N. F. in. p. 119. 512. Woman: left pes bearing an extra digit articulating by an imperfect metatarsal with outside of metatarsal of IV. The extra digit stands obliquely to the others, sloping outwards and being attached by ligaments to the normal V. [The Catalogue states that the extra digit resembles a right digit, but I see no sufficient evidence of this.] C. S. M., Ter. Cat. 312.