The muscles which extend between the head, sternum, and clavicle, together with the muscles of the acromion process of the scapula, make an external covering 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 Bischoff’s 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. Bischoff 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 chimpanzee 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 considerably over the lower segment of the upper portion. In the chimpanzee an upper portion of less firm texture extends from the second to the fourth, and a lower with three digitations from the fourth to the seventh ribs. This second lower portion is sometimes absent. I have seen the upper portion attached to the coracoid process of the scapula, and the lower portion to the ridge of the greater tuberosity of the humerus. In the orang an upper portion, separable into three digitations, extends from the second to the fifth ribs, and is attached to the coracoid process. A lower portion, also separable into three digitations, extends from the fifth to the seventh ribs, and is also attached either to the greater tuberosity of the humerus or to its edge; this latter portion projects below over the pectoralis major. In the gibbon (_Hylobates albimanus_), the upper portion starts from the second, the lower from the third to the fifth ribs. It may here be remarked that the pectoralis minor is in man also sometimes separable into digitations, which may be connected both with the coracoid process and with the capsular ligament of the shoulder-joint. In anthropoids the tendon of insertion of this muscle is remarkably slender.