ANATOMICAL STEUCTUEE OF ANTHROPOID APES. 161 



ternal coveriHg to the throat-pouch, which I shall 

 describe presently. The pectoralis major of the 

 gorilla, as well as that of man, divides into two 

 portions, one attached to the clavicle, the other to 

 the cartilages of the true ribs. The former is divided 

 from the deltoid by a wide interval, filled with 

 connective tissue and fat. But both portions of 

 the pectoralis major are divided by a tolerably 

 wide space, into which, in Bischofifs opinion, the 

 throat-pouch is inserted. This, however, I do not 

 believe, since that organ would be compressed and 

 strangulated between the two portions of muscle 

 whenever they were exercised. It may, however, 

 be supposed that room for an enlargement of the 

 throat-pouch when the animal is bellowing is 

 afforded by the existence of these spaces. Bischofif 

 is right in the assertion that the clavicular portion 

 of the pectoralis major is wanting in the orang- 

 utan. The upper part of this muscle springs 

 directly from the sternum. The lower sternal ribs 

 give origin to the pectoralis minor. The chim- 

 panzee and gibbon display clearly in this muscle 

 the separation we have mentioned into a clavicular 

 and a sternal portion. 



The structure of the pectoralis minor in these apes 

 is full of interest. In the gorilla it divides into an 

 upper portion of firmer tissue, less easily separable 

 into digitations, which arises from the third to the 

 fifth ribs, and a lower portion, separable into three 

 digitations, of which the upper segment laps con- 

 siderably over the lower segment of the upper portion. 

 In the chimpanzee an upper portion of less firm 



