84 NATURAL HISTORY OF 



and almost prevents the perfect extension of the leg 

 on the thigh.* " The motion of the knee-joint in the 

 black orang was free backwards, but the annual does 

 not seem capable of perfect extension of this joint, from 

 the contraction of the posterior muscles of the limb." t 

 Continuing the organization of the lower extremity, 

 we shall now examine the foot. In man, the whole 

 surface of the tarsus, metatarsus, and toes, rests upon 

 the ground, and the os caleis forms a right angle with 

 the leg. In the orangs, this bone begins to form an 

 acute angle with the limb, and consequently does not 

 rest upon the ground. The sole of the foot becomes 

 narrower ; and in all the attempts at erect progression, 

 exhibited by the orangs which have been shown in 



Dr Trail. 



J- " The most remarkable muscle about the top of the thigh, has 

 not been noticed by Tyson, Camper, Cuvier, or the older anato- 

 mists. It is a flat triangular muscle, arising from the whole anterior 

 edge of the ileum to. within half an inch of the acetabulum, and is 

 inserted just below the fore part of the great trochanter, between 

 the head of the cruralis and vastus externus, a little below tlie 

 origin of the former. It is thin and fleshy through its whole 

 extent, except where it is inserted by a very short flattened tendon. 

 At its upper part it is united by* cellular substance to the iliacus 

 internus. The action of this muscle appears to be intended to 

 aeiyist in climbing. On this account, we propose to name it the 

 scaadens, or musculus scansorius ; and we are disposed to regard 

 it as one of the principal peculiarities in Simla satyrus." DR 

 TKAIL. Account of Slack Orang. Worn. Soc. Traaa. Vol. 

 iii. p,29. 



