GOO 



bodies of nerve cells), an increase going on, sj'stematieall}', with 

 increasing quantity of the entire brain, does not appreciably corrupt 

 those results. 



It was this consideration that induced Dhéké and Lapicque to 

 investigate the chemical composition of the brain in large and small 

 dogs. ^) From their results it is obvious that the real disproportion 

 between the two constituents in large and small brains of nearly 

 related animals, though existing, is insignificant when compared 

 with what it seems to be on sections of those brains and from super- 

 ficial mathematical reflection. We may infer that the seemingly very 

 striking disproportion is, to a very large amount, corrected by other 

 variations going hand in hand with augmentation of the quantity 

 of brain, namely increasing thickness and folding of the cortex and 

 less rounded form (i.e. relatively more extended surfaces) of the 

 larger brain, these three processes (or two in the brains without 

 folding) tending to increase the relative amount of grey substance. 



The positive knowledge, obtained in this way, of the relation 

 between quantity of brain and size of tlie body, in species and indi- 

 viduals, gives now a meaning to that "puissance étrange" 0.55.. and 

 at the same time 0.?2.. by which those relations are determined. 



Referring to the arguments in my memoir of 1897 on the peculiar 

 relation of the eye to the size of the body, and continuing the 

 analysis of the exponent 0.56 or 0.55,., I believe that it will be 

 easy to prove its rational character, as well as that of the exponent 

 0.22 .. In this way the correlations we found are raised to the 

 rank of real biological laws. 



In the memoir of 1897 I had already pointed out that the factor 

 that expresses the deviation from the simple relation between weight 

 of the brain and superficial dimension of the body is the cube-root 

 of the linear dimension of the body. 



^0.55... (.^:^n be analysed as follows: 



2 1 - + - 



^. ,SO-66 — 0.11 — ^T ~"¥ B. aS0 22 + 0.33 — ^9 9 



The relations found above can then be described as follows: 



1. In species of Vertebrates that are alike in the organisation 



Ï) "Sur le rapport entre la grandeur du corps et la développement de l'éncé- 

 phole." I.e. (1898). 



