648 



in tliis wa}' the required measure for the organisation of t!ie 

 nervous system cannot be found, but on tiie contraiy false relations 

 are obtained. Then Man is indeed not only inferior to some small 

 Monkeys but even to the Mouse. The latter would then be four 

 times better provided with brain than the Brown Rat, and the Cat 

 five times better than the Tiger or the Lion. 



In general we find, not only in Mammals, but in all Verte- 

 brates, that the smaller species of closely allied animals, relatively 

 to the weight of their bodies, have a great quantity of brain. 



If we exclude, however, as much as possible, the above mentioned 

 factors which, besides the size of the body, influence the quantity of 

 brain, if we thus compare animals taken in the state of nature, 

 which are as near as possible to one another, systematically, in their 

 manner of life and in the shape of their bodies, but differ as much 

 as possible in the size of their bodies, then it must be possible, 

 to discover at least, if it is not a simple proportion, some relation 

 existing between the quantity or mass of brain and the size, the 

 weight of the body. 



About twenty years ago the necessary, trustworthy evidences, 



chosen and explained with critical discernment, were very rare. 



Thankfully it may be remembered here that it was Max Weber, who, 



'by procuring them, was one of the first that prepared the way for 



the treatment of this problem, at least in so far as regards Mammals ^). 



At all events the size of the body remains a very important 

 factor amongst those determining the quantity of brain, for the Lion 

 e.g. possesses absolutely 7 limes as much brain as the Cat, the 

 Brown Rat 6 times as much as the Mouse. Evidently the weight of 

 the brain is, after all, a (mathematical) function of the weight of the 

 body. If the quantity of brain does not increase proportionally to the 

 volume of the body, expressed by the weight, it might be that this 

 is really the case with regard to the superficial dimensions, as being 

 proportional with the receptive sensitive surfaces and with the sections 

 of the muscles, thus measuring the passive and active relations of 

 the animal to the outer world, for which in this way the quantity 

 of brain can be a measure. Then, in animals equal in organisation 

 and shape, but not in size, the quantities of brain must increase as 



the — power or the power 0.66.. of the weights of the bodies. 



In those comparable Vertebrates of different sizes the longitu- 

 dinal dimension might likewise be the measure of the quantity of 



1) Especially in his "Vorstudien über das Hirngewichl der Saugethiere". Fest- 

 schrift ftlr Carl Gegenbaur. Leipzig 1896. 



