The Myology of Chimpanzee and Baboon. 443 
MeMurrich (’03) shows that the sublimis has been differentiated 
from a common flexor mass similar to that found in Monotremes 
and, little by little, has developed until it includes all che condy- 
lar portions of the original muscle. In the chimpanzee, the further 
development of a radial origin does not seem to be constant. 
Even in man, this origin is variable and may be wanting. Com- 
plete separation of the divisions for the digits is also found (Le 
Double). (See table IT.) 
The Flexor digitorum profundus (perforans) arises in the chim- 
panzee (I) (a) from the oblique line of the radius internal to the 
origin of the second head of the sublimis, and (b) from the radial 
half of the interosseous membrane; it also arises (II) (a), from the 
dorsal surface of the ulna along its upper two-thirds by an aponeu- 
rotic septum between it and the flexor carpi ulnaris, (b) from the 
proximal half of the under surface of the ulna, and (c), from the 
ulnar half of the interosseous membrane. The radial head (qa) 
supplies a large perforating tendon for the second digit; the fibers 
are inserted upon the radial border of this tendon. This belly cor- 
responds in its origin to the flexor pollicis longus in man, although 
in my chimpanzee, no connection can be found between this divis- 
ion and the thumb. However, a fine tendon is found arising from 
the annular ligament and from the surrounding palmar fascia, 
which is inserted into the terminal phalanx. Such an insertion 
would correspond to that of the flexor pollicis longus in man. 
As there was no muscle connected with this tendon, it seems that 
there could have been no flection of the terminal digit. Le Double 
although never himself finding the flexor pollicis longus lacking in 
man, cites Gruber, Wagstaffe, and Fromont as having found a 
ease each where this muscle was represented by a thin tendon 
from the sesamoid bone of the metacarpo-phalangeal articulation 
co the terminal phalanx. The tendons for the third and fourth 
digits extend far up into the fibers from the ulnar origin. They 
show a tendency to divide into threads and two bellies are 
closely associated all the way down. Just after leaving the annu- 
lar ligament, the tendons are joined by a strong transverse sheet 
of tendon 3 em. broad, from which arise two of the lumbricales. 
The division for the fifth digit also arises from the ulna as a small 
