NOTES ON THE MYOLOGY OF ANTHROPOPITHECUS 
NIGER AND PAPIO-THOTH IBEANUS 
E. C. MacDOWELL 
WITH FIVE FIGURES 
Through the kindness of Dr. Spencer Trotter, professor of 
biology at Swarthmore College, I have been afforded the oppor- 
tunity of dissecting a female chimpanzee, Anthropopithecus niger, 
which had just lost her milk dentition, and an adult male baboon, 
Papio-thoth ibeanus. The notes from these dissections were used 
by Dr. Trotter in May, 1908, as the basis of a communication to 
the Academy of Natural Sciences of Philadelphia. 
It is my plan to describe certain muscles in these two forms, 
which are found to differ from the conditions normal in man, and 
to compare these with the results of previous investigators. 
I wish to express here my appreciation of the many sugges- 
tions and the valuable assistance rendered by Dr. Trotter in the 
preparation of this paper. 
MUSCULATURE OF THE UPPER LIMB 
A. MUSCLES OF THE SHOULDER 
The Pectoralis Major in the chimpanzee, is divided into three 
parts which are not absolutely differentiated: (a) pars abdominalis; 
(b) pars sternalis; and (c) pars clavicularis. The first (a) arises 
from an aponeurosis with the rectus abdominus at the level of 
the seventh rib and from the sternum as far up as the third rib. 
It is inserted into the humerus, 3 em. distal to its head, by a thin 
tendon, composed of loose fibers. This is covered by the more 
proximal border of the insertion of the pers costo-sternalis. The 
second part (6) is the most highly developcd division of the group. 
It arises from the sternum and the sternal ends of the costal carti- 
lages of the first, second, and third ribs. Its fibers are inserted 
