The Myology of Chimpanzee and Baboon. 433 
and a sternal part. In an orang, -Duvernoy describes two parts, 
the sterno-clavio-humerale and the sterno-humerale, where as in a 
chimpanzee he found no divisions. Beddard found no connection 
with the clavicle in his orang. Owen describes three muscles in 
place of all the pectorals, namely the sterno-humeralis, costo- 
humeralis, and sterno-costo-humeralis. 
The Pectoralis minor arises in the chimpanzee along a line 
extending from the first to the fourth ribs, 2 em. from the sternum 
at its anterior, and 5 cm. at its posterior end. The muscle is 
divided into two separate digitations; the posterior digitation is 
subdivided into three. All the fibers quickly converge to the 
strong, round tendon, which is half as long as the muscular part. 
This is inserted into the capsule of the shoulder joint. 
In my baboon and in a small Macacus monkey, the pectoralis 
minor is more developed. Distally it extends as far as the pec- 
toralis major does in the -first case, and in the second, from the 
second rib to the sixth. In both forms, it arises from the sternum 
itself and from the sternal ends of the costal cartilages; whereas, 
in man, it arises from the ends of the ribs themselves, thus form- 
ing a much less powerful muscle. 
Champneys and Hepburn describe this muscle in chimpanzees 
as arising from the upper three ribs, and being inserted into the 
shoulder joint. Duvernoy did not find it divided into distinct 
parts. In the orang, Beddard found two parts, one from the third 
and fourth ribs, the other from the fourth, fifth and sixth. Hart- 
mann describes the condition in the chimpanzee very much as I 
found it. His orang corresponded with Beddard’s description. 
Primrose found the tendon of this muscle, in his orang, extending 
to the coracoid process, whence two ligments were traced to the 
head of the clavicle and to the acromion process, respectively. 
This was a new condition. Bardeen considers the insertion into 
the head of the humerus within the capsule, normal in primates 
below man. Ina gorilla, Douvernoy describes this muscle (called 
by him ‘‘costo-caracoidien”) as having two parts, one with six 
digitations inserted into the coracoid process, the other with two 
digitations joined to the short portion of the biceps after its inser- 
tion into the coracoid process. 
THE AMERICAN JOURNAL OF ANATOMY. VOL. 10, No. 3. 
