ANATOMICAL STRUCTURE OF ANTHROPOID APES. 171 



common to the fingers, and enlarged in the region 

 of the third and little fingers. A superficial flexor, 

 belonging to the index finger, started from the 

 inner condyle of the humerus, and from the back of 

 the inter-muscular septum. The deep finger-flexor 

 was attached to the four fingers. In the orang the 

 first of these flexors forms a two-tendoned belly 

 for the index finger, as well as one for the other 

 three fingers. The deep flexor only displayed two 

 bellies. In the gibbon, on the other hand, the 

 superficial flexor displays four bellies. 



In the carpus of the chimpanzee there is, so far at 

 least as my experience goes, a so-called sesamoid 

 bone. It is in this instance in connection with 

 the scaphoid and trapezium bones, just where the 

 fibres of the anterior and posterior ligaments of the 

 wrist pass into each other. In the chimpanzee the 

 tendon of the long abductor muscle of the thumb 

 sends some fibres into this sesamoid bone, while the 

 other fibres of the tendon of this muscle, which 

 divides into several strips, are inserted in the 

 trapezium bone, and a few also in the base of the 

 first metacarpal bone. 



The short flexor muscle of the thumb, of which 

 Bischoff has denied the existence, is certainly 

 present in these animals. In the chimpanzee the 

 lower fibres of the short abductor muscle of the 

 thumb have their origin in the sesamoid bone. 

 The middle fibres, of the same muscle issue from 

 the strips of ligament attached to the sesamoid 

 bone. On the other hand, the upper part of the 

 muscle has its origin in the anterior annular liga- 



