Comparative Myology of the Chimpanzee. 361 



Brachialis anticns, and much higher than in man ; while 

 this disposition of the flexors mars the symmetry of both 

 elbow and knee ; combined with the constant partial flex- 

 ion of the arm and leg it confers upon the ape greater 

 j-eadiness and power of contraction. The length of the 

 belly of the Supinator longus is to that of the tendon as 

 five and a half to one and a fourth. 



From the direction of the force, the Supinator longus is 

 a very feeble supinator, much more so than the Biceps, 

 which also can turn the palm fairly upward, while the for- 

 mer can only bring the thumb or radial side of the hand 

 uppermost ; then continuing to act, it is a simple flexor of 

 the forearm, with of course more power the higher it is 

 attached upon the humerus ; in fact the Supinator longus 

 bears the same relation to the humerus when the hand is 

 fixed, as in climbing, that the Biceps bears to the forearm 

 when the shoulder is the fixed point. Both muscles may 

 act as either flexors or supinators ; in the former case their 

 effect as supinators must be counteracted by the Pronator 

 teres, which then is also a flexor, and in the latter case the 

 Triceps may be felt to contract to prevent flexion, and also 

 to fix the ulna. The gradual disappearance in the Quad- 

 rumana of the power of rotating the forearm, which is so 

 complete in man, is well described by Vrolik (7, page 30). 

 The most natural, and therefore the most useful position 

 of the forearm in the climbing Quadrumana, is midway 

 between pronation and supination, when the Supinator 

 acts freely as a flexor. While dissecting an Angora goat 

 last winter, I was much interested to observe that the Biceps 

 had two distinct tendons of insertion, of which one, repre- 

 senting the single tendon of man and in the Quadrumana, 

 ran round the neck of the pronated radius, to be attached 

 to its lower surface, while the other extra tendon was in- 

 serted at once into the upper border of the bone ; this 

 double tendon, adapted to the flexion of the forearm in its 



JOURNAL B. S. N. H. 46 AUGUST, 1861. 



