184 ZOOLOGY. 



instinctive faculties are present or absent in certain animals, 

 nor of the mechanism by means of which the faculties are exer- 

 cised; all we know is, that it is by means of the nervous system 

 that all these faculties are exercised. When the action of the 

 brain is suspended, we lose the consciousness of our existence, 

 and with it all the intellectual faculties : the organic life then 

 alone remains: thus the brain is proved to be the organ 

 of all intellectuality, and the centre of " the life of relation." 

 Since nothing is known as to the nature of thought, we are 

 of necessity compelled to refer it to an immortal principle in 

 man called the soul ; in other animals, the vital principle seems 

 to take its place. 



341. The brain being admitted to be the instrument by 

 which the intellectual faculties are exercised, it is natural 

 to suppose that its structure, or at least its structural arrange- 

 ments, will be modified in different animals ; and this is what 

 we find takes place. 



342. Generally speaking, the power of an organ, all 

 things being equal, is in the direct ratio of its bulk ; and to 

 a certain extent this holds true, when we compare the brain 

 of man with the quadrumana, carnivora, and rodents; in 

 fishes, animals low in the intellectual scale, the brain is com- 

 paratively very small and simple. 



This led to the idea, that the amount of intelligence in 

 man and animals might be measured by the size of the brain, 

 and the facial angle, invented by Camper, was used with this 

 view.* 



A horizontal line (c d, Fig. 135) is represented as passing 

 by the auditory canal and floor 

 of the nasal fossae ; a second 

 line, b a, is let fall on the first 

 so as to intersect it ; the angle 

 formed at the point where these 

 lines intersect each other will 

 d be found to measure, by its 

 approach to a right or an 

 obtuse angle, the development 

 of the cranium anteriorly, as 

 compared with the size and 

 protrusion of the face. The 

 angle is called the facial angle of Camper. 



* It is calculated to show the relative size of the cranium as compared 

 with the face ; but Camper did not employ it with this view. E. K. 



