THE EXTREMITIES OF ORYCTEROPUS CAPENSIS. 581 



nent seules la tete du premier metacarpien. Le muscle ne prut done agir directement 

 sur le pouce; il est, avant tout, un muscle de la station." 



May not the above-described insertion of the terminal tiMidon principally into tin 

 trapezium, while but few of its fibres pass to the metacarpal of a pollex which, though 

 somewhat feeble, must still be ranked amonaj the range of digits 1 , either be looked upon 



as the soon-to-be-cast-off appendage of an already useless member, or be regarded in tin- 

 light of a preparation for a yet more rudimentary, or rather decadent, condition of the 

 pollex, such as exists in the Orycteropus, in which animal the sole representatives of 

 this digit are two difficult-to-be-discovered, seemingly insignificant ossicles 2 ? 



In the Guineapig, in which the pollex is absent, the tendon of the extensor oss is meta- 

 carpi pollicis, according to Mr. Mivart and Dr. Muric , "runs on to the base of the 

 metacarpal of the index, though mainly inserted into the rudimentary trapezium." 



According to Prof. Huxley, while the tendon only of this muscle is divided in the 

 Gorilla, Orane, and Gibbon, this division involves the muscle itself in the Chimpanzee 4 . 



Soemmering has noticed in man", besides the simple splitting of the tendon 



d 



*■ 



division of the muscle itself. Theile has recorded that this muscle has sometimes been 

 observed in man to be divided into two parts along its whole extent 6 . 



Extensores primi et secundi intemodii pollicis. — These muscles arc, as might be 



expected, absent. 



Extensor indicts.— Arises from the middle third of the strong internal ridge, or margin, 

 of the ulna, immediately anterior to the insertion of the external portion of the triceps y 

 lying, also, immediately to the outer side of the extensor ossis metacarpi pollicis, at the • 



origin of this latter. 



After this, it rapidly narrows, and its tendon, on reaching the articulation of the 

 radius and ulna, runs under a ligamentous bridge stretching between the adjacent 

 corners of the extremities of these bones, and passes on to the dorsum of the hand, 

 underneath the three branches of the common extensor tendon. At a short distance from 

 its termination, it divides into two slips, which are inserted into the bases of the proximal 

 phalanges of the index and " middle " digit respectively. 



Extensor communis digitorum — Arises from the lower part of the " supinator ridge" of 

 the humerus, overlapping here the lower half of the origin of the extensor carpi radialis — 

 also from the tubercle upon the external condyle, which gives origin to the supinator 

 brevis, being fused at this point of origin with the extensores annularis and minimi digiti. 



Shortly before it arrives at the distal extremity of the radius, the muscle divides into 

 two bellies, which become tendinous on passing under the annular ligament common to 

 them and to the tendon of the extensor indicts. The ulnar tendon, at the carpo-metacarpal 



1 Pouchet remarks, in a kind of preface or introduction, op. cit. p. 3, " Le premier doigt est grOle, un pcu detache 



des autres, mobile. On peut lui donner le nom de pouce:' 



- Cuvier says, " Le premier os du second rang [of the carpus] est un trapeze auquel s'attacheul leux tr -]>• ts os. 

 seuls vestiges du pouce."— Ossemens Fossilcs (nouvelle edit. Paris, 1823), tome v. p. 135. 



3 " On the Anatomy of the Crested Agouti," Proc. Zool. Soc. June 1868, p. 404. 

 Lect. Coll. Surg. See Med. Times and Gazette, 1864 



5 De Corp. Humani Fabr. vol. iii. p. 239. 



6 Encyclop. Anat. (Paris, 1843), tome iii. p. 932, 







