174 ZOOLOGY. 



But if the i ulii.s we have spoken of explain more 

 or |'r >ati>factorily the actions of man and animals, then- 

 are others which, in tlu- existing state of our knowledge, 

 admit of no explanation, and which lead us to suppose that 

 such animals ]>ossess organs of sen>e of a kind unknown to 

 us. Neither instinct nor intelligence can explain the course 

 of the swallow and carrier-pigeon, transported hundreds of 

 miles from their locality, towards which they Hy, when let 

 loose, in a line as straight as if it lay before their eyes. The 

 dog and horse seem to retrace their course, when lost, 

 by the ordinary senses ; but this cannot be the case with the 

 carrier-pigeon flying in a straight line from Bordeaux to 

 Brussels. 



340. Relations between the Intellect and the Brain. 

 We know nothing of the cause why certain intellectual and 

 instinctive faculties are present or absent in certain animals. 

 nor of the mechanism by means of which these 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 tin- 

 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 in 

 them 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 ar- 

 rangements, 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 qnadrnmana, carnivora, and rodents; in 

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

 paratively very small and >imple. 



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

 man and animals might be measured by the si/e of the brain, 

 and the facial angle, invented \>\ C<rntj>( r. was used with this 

 view. [It IS calculated to show the relative si/e of the cranium 

 as compared with the face; but Camper did not employ it 

 with this view U. K.J 



