394 THE SENSORIAL FUNCTIONS. 



brain: but on arriving at Man the continuity of the series is 

 suddenly disturbed by the great expansion of the hemi- 

 spheres, (Fig. 4f)l,) whicli, compared with those of quadru- 

 peds, bear no sort of proportion to the rest of the nervous 

 system. Both Aristotle and Pliny have asserted that the 

 absolute, as well as the comparative size of the human brain 

 is "-rcater than in any other known animal: exceptions, how- 

 ever, occur in the case of the Elephant, and also in that of 

 the Whale, wliosc brains arc certainly of greater absolute 

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

 which we are familiarly acquainted, have brains considera- 

 bly 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 development of the face and jaws. In Man, 

 on the other hand, the bones of the skull rise perpendicu- 

 larly 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 important organ. It is chiefly from the 

 expansion of the hemispheres, and the development of its 

 convolutions, that the human brain derives this great aug- 

 mentation of size.* 



• This will be apparent from the vertical section of the human brain, Fig-. 

 461; where, as before, s is the spinal marrow; ji, the medulla oblongata; c, 

 the cerebellum, with the arbor vitae,- t, the optic tubercles, or corpora quad- 

 rigemina, dwindled to a very small size, compared with their bulk in fishes: 

 p, the pineal gland, supposed by Des Cartes to be the seat of the soul; v, 

 one of the lateral ventricles; a, the corpus callosum; and h, ii, h, the hemi- 

 spheres. 



Several expedients have been proposed for estimating the relative size of 

 the brain in different tribes of animals, with a view of deducing conclusions 

 as to the constancy of the relation which is presumed to exist between its 

 greater magnitude and the possession of higiier intellectual faculties. The 

 most celebrated is that devised by Camper, and which he ternied the facial 

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

 skull, from the car to the roots of the upper incisor teeth, and the other from 

 the latter point, touching the most projecting l^ai-t of the forehead. Cam- 

 per conceived that th.e magnitude of this angle would correctly indicate the 

 size of the brain, as compared with the organs of the principal senses which 



