The Myology of Chimpanzee and Baboon. 445 
The flexor digitorum profundus in the baboon (fig. 2, P) shows 
great consolidation. It arises (a) from the oblique line of the rad- 
ius as far as the pronator quadratus, (b) from the posterior bor- 
der of the ulna, extending from the olecranon process to a point 
8 cm. from the distal and, (c) from the common flexor tendon 
from the internal condyle of the humerus; the fibers from these 
various origins are joined in a broad flat tendon 2 em. wide, which 
extends half way up the arm. It is heavily grooved, indicating 
the elements of the tendons for the digits, but these tendons are 
not differentiated until the tendon reaches the palm. The origin 
(a) from the radius corresponds to that of the flexor pollicis 
longus, which, as in the chimpanzee, is still undifferentiated from 
the profundus. However, a strong round tendon, supplying the 
pollex (fig. 3, 7’), is given off from the common tendon just after 
passing the ligament. 
In a gibbon, Hepburn found an origin of the profundus from the 
internal condyle, which, he says, clearly shows the relation between 
the two flexors. The condylar segment has become the sub- 
limis. ‘The condition in my baboon shows the profundus, in- 
cluding fibers which in the higher forms are included in the sub- 
limis. The separation of the flexors into individual bellies is 
considered, by Bardeen, to be associated with the refinement of 
the movements of the fingers. Champneys, Beddard, and Hep- 
burn found no tendon to the pollex, but name the division to the 
index the flexor pollicis longus, and describe a small tendon given 
off from this to the pollex. Testut calls the separated divisions 
to the index in his chimpanzee a part of the profundus. This agrees 
with MeMurrich’s conclusions that the flexor pollicis longus 
should not be said to be missing in monkeys, nor be described as 
fused with the profundus, but rather as still undifferentiated from 
this muscle. In the chimpanzee, Keith found no tendon to the 
pollex in ten out of twenty-five cases; Vrolik describes a tendon 
from the flexor brevis digitorum that is inserted into the terminal 
phalanx, which seems to take the place of the tendon of the flexor 
pollicis longus. Bischoff found no tendon to the pollex in the go- 
rilla. Henle, Wood, and Turner (quoted by Champneys) observed 
in man a muscular slip from the flexor pollicis longus which sent 
