122 



ANIMAL MECHANICS. 



free. This type, according to Gratiolet, is realized in the 

 Gorilla as well as in the Chimpanzee : the small tendon which in 

 these animals flexes the thumb is reduced to a tendinous thread, 

 which exerts no action, for its origin is lost in the synovial 

 folds of the tendons which bend the other fingers, and it abuts 

 on no muscle. The thumb, therefore, in these apes is won- 

 derfully enfeebled, and in none of them is there a trace of the 

 large independent muscle {Jl. poll, long.) which gives move- 

 ment to the human thumb ; and, far from becoming more 

 strongly developed, the thumb so characteristic of the human 

 hand seems in the most elevated apes ( Orang) to incline to a 

 complete annihilation. These apes have, therefore, nothing 

 in the organization of their hand which indicates a passage 

 into the human form. 



I have never had an opportunity of dissecting the hand of 

 a Gorilla or of an Orang, but I have dissected the hand of 

 the Chimpanzee {Troglodytes niger). In this animal I found the 

 flexor tendon of the thumb to be formed by the union of two 

 small thread-like tendons ; one of which, of silken lustre, was 

 derived from the portion of the jl. dig. sublimis muscle cor- 

 responding to the index finger, and the other, equally slender, 

 but wanting the silken lustre, proceeded from the tendon of 

 the Jl. sublimis of the little finger. 



The peculiarities of the human Jl. poll, longus have always 

 been insisted upon by anatomists as essentially characteristic 

 of Man, as distinguished from the Quadrumans ; but excep- 

 tions of the most startling kind are occasionally met with. In 

 1864, a male subject was brought into the dissecting-room 01 

 Trinity College, one of the hands of which was dissected by 

 Mr. Finny, Med. Schol., who made the following note at the 

 time : — 



"Abnormal Jlexor pollicis longus. The fleshy origin of this 

 muscle from the bone of the forearm was entirely wanting, and 

 the tendon of the Jl. poll. long, was attached opposite to the 



