649 



brain, on acconnt of the segmental structure, and the nio\enient by 

 the contraction of muscle-fibres, working- on levers proportional (o 

 the length of the body in Ihis tribe of animals. 



Again, the extension or the specification of some definite receptive 

 surface (of sense) may likewise determine the quantify of brain. As 

 the foj-mer in its turn must be a (mathema(ical) function of the size 

 of the bodies of animals that are equal in shape and organisation, 

 it must, according to some (arithmetical) power-proportion of the 

 weight of the body, be one of the factors determining the ([uantity 

 of brain. 



However insolvable, at first sight, the problem indicated by the 

 title of this communication may seem to be — as no organ is more 

 complicated of structure and in its physiology more obscure than 

 the brain — in this way it must be possible to make it fit 

 for solution. It must, at all events, be possible, likewise for 

 groups of animals of different grades of organisation, to repre- 

 sent the cephalLsaflon by figures, and thus to compare them. 



Be r the required exponent of correlation (iudicaling the corre- 

 lation of the brain quantity to the mass of the body), be e (ence- 

 phalon) the weight of the brain, .s (soma) the weight of the body of 

 the smaller animal, E and >S the weight of the brain and the 

 weight of the body of the larger animal and k (kephalisation) the 

 coefficient of cephalisation, equal for both, then we have the following 

 equations : 



E : e =^ k S'' : ks'' 

 E:e — S'-. s'- 

 'S\- _ E 



e 

 log E -log e 



log S' log s 



, = E = i 



S'- s'- 

 When working these equations by evidences contributed by Mw 

 Weber and others I found in 1897 ^) at a seven times repeated 



1) The proportion of the weight of the brain to llie size of the body in Mammals. 

 Verhandelingen der Kon. Akademie van Wetenschappen te Amsterdam. Volume 

 5. No. 10. Amsterdam 1897. 



Also in French and German text : Sur le rapport du poids de Tencépbale 

 avec la grandeur du corps cliez les Mammifères. Bulletins de la Sociélé dAn- 

 thropologie de Paris 1897. p. 337-37G. 



Ueber die Abhangigkeit des Hirngewiclites von der Körpergrösse bei den 

 Sangetliieren. Archiv lür Anlhropologie. IJaiid 2.j. Helt 1 und 2. Braunschweig 

 J897, p. 1—28. 



