The Myology of Chimpanzee and Baboon. 447 
nycticebus tardigradus, there is no separate flexor pollicis longus in 
any of the monkeys. He believed that this is an important dis- 
tinction between man and ape; however, he does not believe with 
Gratiolet and Alix that its separation in man and blending in apes 
is any hindrance to the evolution theory. For he had found in 
human examples all the main types of the coalescence of this mus- 
cle, as variations. Dally also answered Gratioles by arguing that 
if man did not use it, this muscle would soon become undeveloped. 
He believed that the development of this muscle has come with 
civilization, and that it was far less developed in primitive man. 
In the chimpanzee, the Abductor pollicis longus (extensor ossis 
metacarpi pollicis) arises from the interosseous membrane, and the 
intermuscular septa between it and the extensor carpi radialis 
brevis and the extensor indicis proprius. It gives off two tendons: 
one of these is inserted into the trapezium, the other into the base 
of the metacarpal bone of the thumb. No sesamoid bone is found 
in its tendon. 
Beddard describes a similar division and insertion in his chim- 
panzee. In man, these same conditions are found at times, which 
closely connect the hand of man to that of the ape (Le Double). 
In a gorilla, Duvernoy describes these divisions as the cubito-sus- 
metacarpien and the cubito-sus-trapezien. Hartmann quotes 
Bischoff as saying that the long abductor in the orang and in the 
baboon is as in man, but that division is found in the gorilla, 
chimpanzee, and macacus. It cannot be said that one of these 
tendons belongs to the extensor pollicis brevis, for Hartmann, Duv- 
ernoy and Vrolik have found an extensor pollicis brevis coexisting 
with a ‘‘cubito-sus-metacarpien’’ which was inserted into the 
metacarpal of the thumb. 
The Ealensor digitt quints proprvus in the chimpanzee arises from 
the ulna below the origin of the extensor digitorum communis. 
The fibers are inserted into a strong, flat tendon that passes 
through a special compartment of the annular ligament, to be 
inserted into the fascia covering the second phalanx of the fifth 
digit. It seems correct to name this the special extensor of the 
fifth digit, since in its origin and in its passage through the liga- 
ment, as well as in its insertion, it corresponds to this muscle in 
main. 
