NERVOUS SYSTEM OF VERTEBRATA. 503 



than that of man. But all the large animals, with 

 which we are familiarly acquainted, have brains 

 considerably smaller ; as will readily appear from 

 an examination of their skulls, which are narrow, 

 and compressed at the part occupied by the brain; 

 the greater part of the head being taken up by the 

 developement of the face and jaws. In Man, on 

 the other hand, the bones of the skull rise perpen- 

 dicularly from the forehead, and are extended on 

 each side, so as to form a capacious globular cavity 

 for the reception and defence of this most impor- 

 tant organ. It is chiefly from the expansion of 

 the hemispheres, and the developement of its con- 

 volutions, that the human brain derives this great 

 augmentation of size.* 



Several expedients have been proposed for esti- 

 mating the relative size of the brain in different 

 tribes of animals, with a view of deducing conclu- 

 sions as to the constancy of the relation which is 

 presumed to exist between its greater magnitude 

 and the possession of higher intellectual faculties. 

 The most celebrated is that devised by Camper, 

 and which he termed the facial angle, composed of 

 two lines, one drawn in the direction of the basis of 

 the skull, from the ear to the roots of the upper 

 incisor teeth, and the other from the latter point, 



* This will be apparent from the vertical section of the human 

 brain. Fig. 461; where, as before, s is the spinal cord; m, the 

 medulla oblongata; c, the cerebellum, with the arbor vita ; t, the 

 optic tubercles, or corpora quadrigemina, dwindled to a very small 

 size, compared with their bulk, in fishes; p, the pineal gland, sup- 

 posed by Des Cartes to be the seat of the soul ; v, one of the lateral 

 ventricles ; q, the corpus callosuni, or principal commissure ; and 

 H, n, H, the hemispheres. 



