i6 THE POPULAR SCIENCE MONTHLY. 



the class of mammals, exclusive of man, was as 1 to 186. My own 

 observations accord very closely with those of Leuret. I found that 

 in the prairie-wolf the proportion between the brain and the body was 

 as 1 to 220 ; in the wild cat, as 1 to 158 ; and in the rat, as 1 to 132. 



If these figures teach anything at all, it is that there is no definite 

 relation existing between the intelligence of animals and the absolute 

 or relative size of the brain. It is true that, taking the data collected 

 by Leuret as the basis, there is a well-defined relation between the 

 mental development and the brain, as regards the several classes of 

 vertebrate animals ; for in fishes, the lowest, the brain is but one 

 5,668th part of the body ; in reptiles, the next highest, it is one 1,321st 

 part ; in birds, next in the ascending scale, it is one 212th part ; and 

 in mammals, the highest of all, one 186th part. There is, therefore, 

 beginning with the lowest class, a regular ascent in the volume of the 

 brain till it reaches the maximum in mammals. 



But, when we look at the relation as it exists between the different 

 orders and genera of any one class, we can not say that there is any such 

 variation in the degree of mental development as we should expect to 

 find if the brain were the only source of the intelligence, and some 

 members of the very lowest class have relatively larger brains than 

 certain animals of the very highest. Thus, the brain of the bass is to 

 the body as 1 to 523, while in the horse it is but as 1 to 700, and in the 

 ox as 1 to 750. If the relative size of the brain is to be taken as an 

 indication of the degree of intelligence, we must regard the bass as a 

 more intellectual animal than either the horse or the ox. The lizard 

 has a brain which bears the high proportion to the body of 1 to 180. 

 This is greater than that existing in the fox, the dog, the sheep, and 

 several other mammals. The canary-bird and the Arctic sparrow have 

 brains proportionately larger than those of any other known animals, 

 including man, and yet no one will contend that these animals stand 

 at the top of the scale of mental development. Man, who certainly 

 stands at the head of the class of mammals, and of all other animals, 

 so far as mind is concerned, rarely has a brain more than one fiftieth 

 the weight of the body, a proportion which is much greater in several 

 other mammals, and is, as we have seen, exceeded by many of the 

 smaller birds. 



Even in absolute weight, independent of any relation to the rest 

 of the body, the brain of man is not the largest, being exceeded by 

 that of the elephant and the whale. But, when we inquire into the 

 matter of the absolute and relative quantity of gray nerve-tissue, we 

 find that in this respect man stands pre-eminent ; and it is to this fact 

 that he owes the great mental development which places him so far 

 above all other living beings, for it is the gray tissue which originates 

 mind — the white, as is well known, serving only for the transmission 

 of impressions and impulses. Unless regard is paid to this point, 

 >^e should certainly fall into serious error in determining the relation 



