251 



in short for all the Vertebrata, and also for the Invertebrata. At 

 birth the brain weight of Man is Ve. ^"<^ i" ^^^^ adult slate of the 

 body 1/47 of the body weight. At its birth a dachshund has 1/29, anf' 

 in the adult state Vi35 of its weight in brains. With a body weight 

 of 7 grams the Brown Rat has less than ^'lo, and when it is full 

 grown 1/160 of its weight in brains. In the Bull Frog of 4V, grams 

 of body weight, the brain weight constitutes '/loo of it, and when 

 the body weight has increased to 200 grams, the ratio of the brain 

 weight is only ^/looo- This gives the skulls, of them all in their first 

 youth, a much more humanlike appearance than they have in the 

 adult state. The great resemblance of the skull of young Apes with 

 that of Man cannot, therefore, have the special significance that is 

 sometimes ascribed to it. 



The peculiarity of the nerve cells manifested in this early cessa- 

 tion of cell division in the ontogenetic growth, now accounts also 

 for the long interruptions in the |>hylogenetic growth, (also resting 

 on cell division), especially if this growth is stronger in certain parts 

 of the biain and mostly in those with the highest integrative action. 

 This phylogenetic growth then takes place with long intervals, as 

 shown anatomically in the brain quantities of allied heteroneuric 

 species of the present animal world, paleontologically by comparison 

 of animal forms of the present time with those of a former world oider. 



But why are the nerve cells distinguished in this conspicuous way 

 from all other cells, with the exception of the muscle cells, which 

 act under their influence? We find the volume of the nerve cells to 

 be in a particular, in what precedes not yet causally explained relation 

 to the body weight. What is the meaning of that "strange" ^/is power? 

 To a proportionality with the V18 or V3 power of the body weight, 

 i.e. with tlie linear dimension of the body, we could readily ascribe 

 a dynamic significance; as the mass of the body increases as P, 

 the physiological cross-sections of the muscles, which determine 

 the muscular force, the sensual areas, the areas that determine 

 metabolism increase only proportional to P*/», it would be compre- 

 hensible if this inadequacy implied an increase of the volume of 

 the nerve cell proportional to PV». But this takes place in a definite, 

 smaller pioportion, according to PVi8. 



In order to detect the meaning of this latter proportionality 1 

 examined on a former occasion ') in what relation the volumes of 

 the principal constituents of the nerve cell, the nucleus and the 

 plasma, are to each other and to the body weight. The result 

 of this examination is recorded in Table W. 



1) These Proceedings, Vol. XXll, p. 671-675. (1920). 



