THE ANTERIOR LIMBS. 125 



the Aquatic C'hevrotain (Fiof. 82, k). With rc<rard to the external stylet, it is 

 an atrophied metacarpal ; for in some teratoio^ ical instances it becomes elongated, 

 and supports a more or less perfect digit. In addition, in the Chevrotain it is 

 replaced by the metacarpal and a complete digit (Fig. 82, e). It is the same 

 with the internal stylet, which is usually smaller, and embedded in a fibrous cord 

 running along the large metacarpal ; it may, like the external stylet, be converted 

 into a perfect metacarpal (Fig. 82, p and g). 



It remains to demonstrate the virtual existence of a fifth metacarpal. Nor 

 mally, no traces of it are found in the domestic Ruminants, but it appears in 

 some anomalies. The museum of the Toulouse Veterinary School possesses the 

 hand of a Lamb, in which it can be seen, inside the internal stylet, which has 

 been transformed into a long metacarpal — a small styliform bone which is 

 assuredly nothing else than the metacarpus of the thumb ( Fig. 82, f, i.). Here 

 is the metacarpus brought to the pentadactylous type ; now for the phalangeal 

 region. 



The digital region of Ruminants presents two perfect digits (the second and 

 third, Fig. 82, d), and two rudimentary digits reduced to one or two small 

 phalanges covered by a horny plate (ergot), situated behind the metacarpo- 

 phalangeal articulation. The two rudimentary digits may, in certain cases, be 

 reproduced — to the right and left of the normal ones — complete and suspended from 

 real metacarpals. This was seen in a specimen from a young sheep (Fig. 82, g) ; 

 and this condition is normal in the Chevrotain (Fig. 82, e), only the lateral 

 digits are less voluminous than those appertaining to the principal metacarpal. 

 The presence of the fifth digit is normally indicated, according to Joly and 

 liavocat, by a tuft or spike of hair inside the carpus, rather above than below it. 

 Sometimes it is better marked ; for in the specimen sho\\Ti in Fig. 82, f' a, 

 where the metacarpal of the thumb had appeared, this digit was represented on 

 the surface of the skin by a plate of horn in the form of an ergot (f, a and b, 

 2). Otherwise, in order to dispel all doubts, it may be mentioned that GeolTroy 

 Saint-Hilaire studied a new-born Lamb which had five digits in the anterior 

 limb. 



6. SoUpeds. — In Solipeds, there is apparently only one digit enclosed in one 

 hoof. Nevertheless, by the aid of analogous facts to those which have already 

 assisted us in proving pentadactylism in Ruminants, we shall be able to demon- 

 strate that the hand of the Horse, Ass, etc., is no exception to the general law. 

 Many anatomists only describe seven bones in the carpus of the Horse — four in 

 the upper row, three in the lower. But it is not rare to see a pisiform bone on 

 the inner side of the trapezoid, which raises the number of carpal bones to eight. 

 And Bourgelat, Girard, Rigot, and Goubaux have observed in the carpus of the 

 Horse, in addition to the bones mentioned, a similar piece alongside the external 

 bone of the second row. Lavocat considered this second piece as the first of the 

 inferior carpal bones — the base of the external digit, and that the bone found 

 beside the trapezoid was the trapezium or base of the internal digit or thumb, 

 the trapezoid being the base of the fourth finger. The trapeziimi and trapezoid 

 are shown, with the significance attributed to them by Lavocat, on the carpus 

 represented in Fig. 82 (l r/, 1, 2). 



The carpus of Solipeds does not dilfer, then, from the archetype, except in the 

 frequent abortion of the fifth superior carpal bone, and the first and fifth of the 

 lower tier. 



The metacarpus of Solipeds comprises a large bone articulating with the 

 11 



