146 LLOYDS NATURAL HISTORY. 



bone is often shorter than the fore-arm. The radius and ulna 

 can be completely rotated. The articulating surface of the 

 trapeziU7fi, the wrist-bone {carpus), to which the thumb is 

 attached, has a rounded face like that of the enfo-ameifor?n 

 bone in the ankle {tarsus), a form which, as already pointed 

 out (Vol. I., p. 11), was in the Lemuroids correlated with an 

 opposable great-toe, so here it is correlated with a true oppos- 

 able thumb. In the Monkeys and Lemuroids this bone is not 

 generally rounded, and they have not the thumb opposable in 

 the strict sense that it is among the higher Apes. 



The thigh-bone {femur) is shorter than the arm-bone 

 {hu7?ierus) ; and the foot is very long ; yet the absolute 

 length of the tarsus is never so great as in Man ; it is the rest 

 of the foot which is so much longer relatively in Apes. The 

 efito-cuneiform, or articulating bone of the ankle for the great- 

 toe, has a sub-cylindrical surface, which gives a great range of 

 motion to that digit, towards and from the plane of the foot. 



The brain of the Apes closely resembles in general form 

 and structure that of Man ; but the cerebral hemispheres 

 differ in being much elongated and depressed, and the cranial 

 capacity of the skull, which is never less than 55 cubic inches 

 in any normal human subject, is in the Chimpanzee 27^ cubic 

 inches ; in the Gorilla 35 inches ; in the Orang 26 inches ; 

 and in the Gibbons very much less. The cerebrum has its 

 surface richly convoluted ; and its posterior lobes always 

 entirely over-arching the cerebellum, except in the Siamang 

 {Hylobates syndactylus). 



"As to the convolutions, the brains of the Apes exhibit 

 every stage of progress, from the almost smooth brain of the 

 Marmoset, to the Orang and the Chimpanzee, which fall but 

 little below Man. And it is most remarkable that as soon as 



