Muscles of Primates.

This physiological fact agrees with the anatomical results of an extended study in the musculature of primates, especially of man, and Hartmann’s book on Anthropoid Apes supplies abundant evidence of the variations of the muscles of these animals, which are not at all more striking than their differing modes of life would suggest. It would be wearisome to quote all these, but a single muscle may be given as an example of a special ape’s muscle with variable distribu­tion. It is called latissimo-condyloideus and starts from the insertion of the latissimus dorsi and passes along the inner aspect of the humerus for a variable distance. In the baboon and others it goes to be inserted into the inner inter-muscular septum and the internal condyle of the humerus, in the orang to the condyle, and in the gibbon to the centre of the shaft. As to origin it proceeds from the insertion of the latissimus dorsi, but in the gorilla from the coracoid process of the scapula and from two portions of the pectoralis minor, and is finally attached to the inter-muscular septum between the brachialis anticus and the triceps; in the chimpanzee it divides into an anterior and posterior portion, the former being attached to the inner condyle, the latter to the middle and inner head of the triceps; in the orang it divides similarly, but in one particular example it had an anterior thin portion attached by a slender tendon to the coracoid process of the scapula and a posterior portion arose from the latissimus dorsi; in the white-handed gibbon it arose from the function of tendons from the latissimus dorsi and teres major and was inserted into the fascia between the tendon of the biceps and the brachialis anticus.

Such a divergence as this within the strict limits of an anthropoid muscle, concerned in the various forms of climbing action of these apes, can only suggest an origin from a divergent set of functions and small details in their respective modes of climbing.