372 • Contributions to the 



signed to stand or walk erect, or to rest on one leg, his 

 entire frame is constructed not for those, but for another 

 set of movements which are subsidiary in man, but to the 

 performance of which both skeleton and muscles in the 

 ape are perfectly adapted. 



Quadriceps extensor femoris. The Rectus has but a sin- 

 gle tendon, from the inferior spinous process of the ilium, 

 the tendon from the acetabulum being absent, as in Ateles 

 Paniscus and in a Macacus ; this peculiarity is not else- 

 where mentioned. The Rectus may act as a powerful 

 flexor of the thigh, in which case its extensor power is 

 easily counteracted by the flexors of the leg, which are in- 

 serted so low down as to act at even more advantage than 

 in man. Both this muscle and the scapular head of the 

 Triceps humeri, of which it is the homotype, are obviously 

 of more use to the ape as flexors than as extensors. 



To lessen the jar on striking the earth, and for the more 

 advantageous attachment of muscles, the limbs of most 

 animals, especially those which move quickly, are con- 

 stantly flexed in two or three places ; to support the weight 

 of the body without still greater flexion, the extensors are 

 very thick and strong; in the elephant, however, whose 

 enormous bulk would require supports of perhaps unman- 

 ageable size, the limbs are straight as in man ; but the 

 legs of the ape are constantly bent, and yet his extensors 

 are not even so strong as in man, showing that the greater 

 portion of his weight must be supported by the arms in 

 front. 



The employment of the ape's foot as an organ of pre- 

 hension requires an extent and freedom of motion at the 

 knee far beyond that exercised by man ; the movements 

 must also be more prompt and easily executed ; this is 

 provided for by the low insertion of the flexors on the tibia, 

 and by the length of the fleshy portion of the nmscles, de- 

 priving the ^emi-Mcmbrniiosus and Scmi-Tendinosus of 



