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

*473. Cat having digital series of all feet abnormal, being the specimQn in Mus. Coll. Surg., Teratol. Catalogue, 306 B. Right pes. The digits III, IV and V (Fig. 85, I) are normal and are fashioned as right digits. The cuboid and external FIG. 86. Left inanus of Cat No. 472, shewing Condition IV of the rnanus. cu, cuneiform. dl — d7, digits numbered from the inside, m, magnum, sclu, scapho-lunar. Tp, trapezoid. cuneiform (cb and ect. cu} are also normal. Internally to the external cuneiform there is a long flat bone which is grooved in such a way as to divide it into three parts (cj~3) and each of these bears a digit.

Of these digits, d2 and d3 have each three phalanges, but dl has only two phalanges and may therefore be called a hallux. The digits d* and d3 are fashioned not as right digits but as left digits, and their claws are thus retracted towards the internal side of the second phalanges, which are hollowed out to admit of this. The bones of the hallux are not thus differentiated as right or left, for the claw is not retractile. The navicular is enlarged in correspondence with the presence of the fourth cuneiform element and the astragalus and calcaneum are normal. (Fig. 85, 1). [Condition III of the pes.]

Left pes. This foot is almost exactly like the right. As in it, the digits III, IV and V are normal and are left digits. Internal to this are three digits, viz. a hallux and two long digits with three phalanges which are both made as right digits. The bones of this foot have not been cleaned. [Condition III of the pes.] Right manus. This is formed on the same plan as the manus of the last animal, differing from it in details of the carpus, chiefly in the presence of two separate trapezial elements. The four digits on the external side, II — V are shewn by their claws to be true

right dibits. They articulate in a normal way with the trapezoid. magnum and iinciforin, and are thus clearly II, III, IV and V. Tinmetararpals of the " pollex " and of the double digit corresponding to d* and d* of Fig. 86 articulate with two separate carpal hones of the distal row. The external of these bears a rather thick HM -tatarsus which peripherally gives articulation to t\v<> dibits. Of these the internal is well formed and bears a claw which slides up on its internal side, and thus shews it to be formed as a /£/'£ digit, The other is misshapen in its proximal phalanx which perhaps contains two phalangeal elements compounded together and aborted ; hence the relation of this digit to the symmetry of the limb is not apparent. The claw and last phalanx are well ton i icd. The innermost carpal bone is nearly normal and bears an almost normal " pollex." [Condition IV of the manus.]

Left manus. This foot has not been dissected, but from examination it appears that the digits II, III, IV and V are normal like those of the right manus. As in it, there is a " pollex " with two proper phalanges, but the metacarpal of the " pollex " is in its proximal part united with the metacarpal of an imperfectly double digit corresponding to d* and d3 of Fig. 86. The division between the two parts of this double digit is not so complete in the left manus as it is in the right and from external examination it appears that the phalanges of the two are not separate. There are two claws of which one is rudimentary and the pads of the two are separated only by a groove. There is nothing to indicate whether these digits are formed as right or left digits. [Approaches Condition IV of the manus.]

*474. Cat having supernumerary digits. This specimen belonged to the strain of polydactyle Cats observed by Mr POULTON (see No. 480) and I am indebted to Mr J. T. CUNNINGHAM for an opportunity of examining it. Left manus. Five digits, the normal number. The " pollex " however is a long digit, composed of three phalanges, which reaches very nearly to the end of the index. The claw of this digit is not retracted to the outside of the second phalanx, like that of a normal digit, but to the inside, and the chief elastic ligament is on the inside of these joints instead of being on the outside as in a normal digit.. This pollex therefore may be said to be fashioned as ;i riijht digit, bearing the same relation to the others as a right hml) liears to the left. The flexors and extensors of this digit were fully developed. The carpal series was normal. [Condition II of the manus.]

/»'/;//// Humus. Six digits fully formed, one bearing an additional nail on the third digit from the inside. Ueginning from the outer or ulnar side, there are four normal right digits, placed and formed as V, IV, III and II respectively. Internal to these are two digits, the outermost having three phalanges, being shaped as a l<'ft digit and bearing a minute supernumerary nail in the skin external to the normal nail. The innermost digit has two phalanges, and is formed like a normal pollex, excepting that its claw was very deep and looked as if it were formed from the germs of two claws united and curving concentrically. The carpus as regards number of elements was normal, but the trapezium and trapezoid were both of rather large size, and the pollex articulated partly with the trapezium but chiefly with the downward process on the radial side of the scapho-lunar. [This approaches Condition IV of the manus, but in it the external of the two united digits is only represented by the minute extra nail.]

Left pes. Six digits, each having three phalanges. The three outer digits were formed as left digits, but the three inner digits were shaped like right digits. The internal cuneiform is double the normal size, but is not divided into two pieces. It bears the two internal digits, of which the innermost is ankylosed to it. [Condition IV of the pes.] Compare Fig. 87, II. Right pes. Same as the left, except for the fact that the two internal digits are completely united in their metacarpals and first phalanges, and the cuneiform series consists of four bones, two of which correspond to the internal cuneiform of double size described in the left foot. (Compare Fig. 85, I, c1 and c2.) [Condition IV of the pes, save for the union of the metacarpals of the two internal digits.]

475. Kitten belonging to Mr Poulton's strain (see No. 480) and kindly lent by him to me for examination. The specimen was very young and the carpus and tarsus were not dissected. Left manus. Six digits, all with three phalanges. The two internal digits are separated by a space from the others so as to form a sort of lobe. The claw of the innermost digit is retracted on the top of the second phalanx and not to the side, so that this digit is not differentiated either as a right or a left. The next digit is a right and the four external digits (II, III, IV and V) are normal lefts. [Condition III of manus.]

Left pes. Same as left pes of No. 474 [sc. Condition IV of the pes]. 476. Cat having its extremities abnormal, the property of the Oxford University Museum and kindly lent for examination; bones only preserved. Right pes. Like the left pes of No. 474, but c1 not separated from c*. [Condition IV of pes.] Left pes. Like the right, but c1 separate from c2. [Condition IV of pes.] Right manus. The four external digits II — V normal. The double digit like that of No. 472. The innermost digit with three

phalanges, but the claw not retracted to one side more than to the other. [Condition IV of the rnanus.] Left /nan us. The same as the right. [Condition IV of the man us.] *477. Cat having all extremities abnormal, also the property of the Oxford University Museum. Left pen. Like the left pes of case No. 474 [sc. Condition IV of the pes] represented in Fig. 87, II. l!'»jht pes a peculiar case (Fig. 87, I). The digits V, IV and III are normal right digits. The digit IJ marked 8 in the figure is

I. Ri^'ht pes not truly conforming to any of the Conditions numbered. II. Left pes shewing the ordinary form of Condition IV of the pes. Lettering as in Fig. 85. (From a specimen in Oxford Univ. Mus.) very slightly differenl iated us a right digit, but the excavation on the external side is very sii^lit , and the claw when ret racted is almost on the middle of the second phalanx. The digit 2 of the figure is a left, and internal to it is a three-phalanged digit, of which the claw is not retracted into any excavation. [Not conforming to any of the Conditions specified.]

478. Cat having all feet abnormal, kindly lent to me by Mr Oldfield Thomas. Left pes. Digits V, IV, III normal lefts. The next internally (II) is a threephalanged digit formed as a right. The next is a thick three-phalanged digit with a partially double nail and double pad. This is not differentiated as either right or left. The innermost digit is a two-phalanged hallux-like digit, not differentiated as right or left. [Not conforming to any condition in my scheme.]

Right pes. The same as the left except that the digit II is only slightly differentiated as a left. The next has a double nail, and the innermost is hallux-like as described for the other foot. [Not conforming to any condition of my scheme.] Right manus. As in No. 472. "Pollex" with two phalanges. [Condition IV of the manus.] Left manus. Same as right, but the " pollex " is only represented by a single bone not differentiated or divided into metacarpal and phalanges and bearing no claw. [Approaches Condition IV of the manus.]

479. Cat. A left pes bearing abnormal digits. The digits II, III, IV and V are normal and are true left digits. Internal to these are two metatarsals which are united centrally and peripherally but are separate in their middle parts. These two metatarsals by their common distal end bear amorphous phalanges belonging to three digits. There are two large claws and one rudimentary one. [For details the specimen must be seen.] The navicular bone is divided into two distinct bones, of which one carries the external cuneiform and a small cuneiform for the digit II, the metatarsal of which is rather slender and compressed in its proximal part. The internal part of the navicular bone bears two cuneiforms, one for each part of the united metatarsals. The digits borne by these metatarsals are so misshapen that it is not possible to say anything as to their symmetry. Mus. Coll. Surg., Terat. Catal., No. 306 A. [This specimen does not conform to any of the Conditions of my scheme.]

*480. In the case of the Cat the polydactyle condition has been observed by POULTOX (Nature, xxix. 1883, p. %Q,figs.; ibid., xxxv. 1887, p. 38, figs.} to recur frequently in the same strain. A female cat had six toes on both fore and hind feet. The mother of this cat had an abnormal number of toes not recorded. The grandmother and great-grandmother were normal. Two of the kittens of the 6-toed cat had seven toes both on the fore and hind feet [no 7-toed pes among specimens examined by me]. Many families produced by the 6-toed cat, and among them only two kittens with 7 toes on all feet, but between this and the normal numerous varieties seen. The abnormality is not in all cases symmetrical on the two sides of the body. The pads of the different toes are sometimes compounded together. In some cases an extra pad was present on the hind foot behind and interior to the central pad. The second pad was sometimes distinct from the central pad and sometimes was united with it. [From the figures it appears that the secondary

central pad in the pes bore to the digits internal to the axis of symmetry a relation comparable with that which the chief central pad bears t<> the digits III — V, but the secondary central pad is at a higher level than the primary one.] It was especially noted that the details in the arrangement of the pads were inherited in several instances. The history of the descendants of the 6-toed cat was followed and a genealogical tree is given shewing that the abnormality has been present in a large proportion of them. This was observed in five generations from the original G-toed cat, so that including the mother of the 6-toed cat the family has contained polydactyle members for seven generations. It may reasonably be assumed that in most of these cases the fathers of these kittens have been normal cats and a good deal of evidence is adduced which makes this likely.

It was observed also that some normal cats belonging to this family gave birth to polydactyle kittens. In the later period of the life of the original 6-toed cat she gave birth to kittens which were all normal. I know no case of reduction in number of digits or of syudactylism in the Cat. Increase in the number of digits occurs in Man in many forms. Among them may be distinguished a large group of cases differing among themselves but capable of being arranged in a progressive series like that described in the Cat. These cases are all examples of amplification or proliferation of parts internal to the index of tin1 manus.

Taking the normal as the first Condition, the next in the progress is a hand having the digits II — V normal, but the thumb with thivr phalanges, or as the descriptions sometimes say, "like ;in index." (Condition II.) In the next condition a two-phalanged digit is present internal to the three-phalanged ••thumb." (Condition III.) In the next Condition the digit internal to the three-plmlanged "thumb'' has itself three phalanges. (Condition IV.) A variant from this occurred in the left hand of a child (No. 488) of parent having hands in ( 'ondition IV. In the child the right hand was in Condition IV, but in the left there were the usual four digits II — V, and internal to ih. 'in two complete digits, each of three phalanges, but of these the external had a small rudimentary digit arising from the metacarpus. Hence the hand may be described as composed of two groups, the one containing four and the other three digits.

In one case, \... 4IMI, I he ri^lit hand was in Condition IV, but the left hand was advanced further. For in it the metacarpal of the innermost digit bore a 2-phalanged digit internally to its 3-phalanged digit. This may be considered as a Condition V. The number of phalanges in the digits in these Conditions may be represented thus. The || marks the metacarpal space. (The hand is supposed to be a right.) Distinct from these Conditions are the states sometimes described as ': double-hand." In the full form of this there are eight digits, each of three phalanges. The eight digits are arranged in two groups, four in each group. The two groups stand as a complementary pair, the one being the optical image of the other ; or in other words, the one group is right and the other is left.

Besides the double-hand with eight digits there are also forms of double-hand with six digits, arranged in two groups of three and three. Lastly, there are cases of double-hand having seven fingers, an external group of four and an internal group of three. Thus expressed these cases seem to come very near that mentioned as a variant on Condition IV, but in one and perhaps both of these double-hands there was in the structure of the forearm and carpus a great difference from that found in the only recorded skeleton of Condition IV.

At first sight it would naturally be supposed that these doublehands in one or all kinds stand to the other Conditions in the some relation that Condition IV of the pes in the Cat does to the other polydactyle conditions in the Cat. But the matter is complicated by the fact that the evidence goes to shew that in the human double-hands the bones of the arm and carpus may be modified, and in DWIGHT'S example of seven digits (No. 489) at all events, and perhaps in other double-hands, an ulna-like bone takes the place of the radius, or in other words, the internal side of the fore-arm is fashioned like the external side. In the polydactyle cats the bones of the fore-arm were normal, as are they also substantially in cases of the human Conditions III and IV, which have been dissected. Further, in some of the human cases of eight digits the abnormality was confined to one hand, which is never the case in the higher condition of polydactylism in the Cat, so far as I know. These circumstances make it necessary to recognize the possibility that some at least of the human double-hands are of a different nature from the lower forms of polydactylism. This subject will be spoken of again after the evidence as to the variation of digits has been given (Chap. xiv. Section (4).)

In addition to cases more or less conforming to schemes that can be indicated artseveral which cannot be thus included. These will be duly noticed \\ln-n the more schematic cases have been described. That any of the cases can be arranged in a formal sequence of this kind is perhaps surprising, and the relations of some nt the < Conditions, II and III fur instance, to each other must at once recall the principle seen already in other examples of addition of a member at the end of a successive series of parts, notably in tin ea>e of Teeth (see p. 272). It was then pointed out that \vheu a new member is added beyond a terminal member whose size is normally small relatively to that of the normal penultimate, then the member whieh is normally terminal is raised to a higher condition. Now this same principle is seen in ( 'oiid it ion III of t lie polydactyle manus.

Attention must nevertheless be forthwith called to the fact that a t \vo-phalanged digit1 may be present internal to the thumb (usually arising from it) though the thumb has still but two phalanges. J5ut generally these cases may properly be described as examples of tl/iji/irity of the thumb; and as was well seen in the case of Teeth, any member of a series may divide into two though the rest of the series remain unaltered. Duplicity of a member without reconstitution of the series is to be recognized as one occurrence, and change in number associated with reconstitution of other members especially, of adjacent members, is another. In Teeth and other M eristic series these two phenomena are both to be seen, though as was pointed out (p. 270) they pass insensibly into each other.

Another feature to be specially mentioned in this preliminary notice is the difference in the manner in which the higher forms of polydactylism appears in the human foot from that seen in the human hand. In the hand there is this strange group of cases forming a progress from the normal hand to Condition V, besides the distinct series of double-hands. Polydactyle feet on the contrary do not in Man, so far as they have been observed (with the doubtful exception of Nos. 499 and 500), develop a new symmetry.

CASES OK I'OLYDACTYUSM ASSOCIATED WITH CHANGE OF SYMMETRY. A. l)i<//tx in one Successive Series. *481. Man having a "supernumerary index" on each hand. Left hand. No " thumb" present. In its stead there is a digit having three phalanges whieh "performs its oth'ce." The middle phalanx was abnormally short. The first intermetacarpal space was not great. [Degree of opposability not stated.] Right hand. In addition to four normal lingers there was a three-jointed digit

1 A case in which a .'l-phubniLvd ili^it was placed on the radial side of the pollex is mentioned by WINMJ:, Jam-. Aunt. J'lii/*.. xxvi. p. MO, but has not yet been described. No other such case is known to me. This perhaps should be classed with double-hands. Cp. No. 502. which could be opposed to them and could perform all the movements of flexion, &c. Internal to this three-jointed digit was a rudimentary thumb having only one phalanx and no nail. [Re- lations of metacarpals to each other not particularly described.] GUERMONPREZ, F., Rev. des mal. de I'enfance, iv. 1886, p. 122, fiys. [Left hand Condition II; right hand almost Condition III.]

482. Girl having a three-jointed thumb, resembling a long forefinger. ANNANDALE, Diseases of the Fingers and Toes, p. 29, PI. n. fig. 19. [Condition II.] 483. Man having a thumb with three phalanges on each hand. Feet normal. In the thumbs the metacarpal is 2| in. long; the first phalanx If in., being longer than usual. The second phalanx is longer on the radial side than on the external side, causing the distal phalanx to curve towards the index. On the internal it measures | in., in the middle | in., and on the ulnar side £ in. The distal phalanx is 1 in. long. When the left thumb is straightened it passes ^ in. beyond the joint between the 1st and 2nd phalanx of the index. In the right hand the thumb scarcely reaches that joint. The utility of the thumb is not impaired. A maternal aunt had a similar thumb on right hand. STRUTHERS, Edin. New Phil. Journ., 1863 (2), p. 102, PI. n. fig. 6. [Both hands Condition II.]

*484. Father and three children, each having 3-phalanged thumbs shaped as indices and not opposable. [Full description q.v.] Paternal grandmother had double-thumb. FARGE, Gaz. hebd. de nied. et chir., Ser. 2, ii. 18G6, p. 61. *485. Man having the following abnormalities of the digits. (Fig. 88). Right hand. The number of digits was normal, but the FIG. 88. Right and left hands of No. 485. Right hand in Condition II; left hand in Condition III. (After WINDLE.)

i-adial digit or thumb had three phalanges in addition to the metaearpal, all the articulations being moveable. Relatively to the others their digit was placed as a thumb. Left hand. The digit '•..n-espoinliiig with the thumb was composed of three phalanges like that of the right side, and though Hnger-like in form it was functionally a thumb. On the radial side of this 3-jointed digit thenwas a supernumerary digit composed of two phalanges articulating with the nietacarpal bone of the 3-jointed thumb. This supernumerary digit had a well-formed nail. The 3-jointed thumb of the left hand was longer than that of the right hand (measuremeiits given), WINDLE, B.C. A., Journ. of Anat. xxvi. 1891, p. 100, PI. II. [Right hand, Condition II ; left hand, Condition III.]