Physiology". — " The Supiifjcduce of the Size of the. Neurone (ind 

 its Parts.'' By Prof'. Eug. Dubois. (Communicated bj Prof. H. 

 Zwaardemaker.) 



(Communicaled in the meeting of October 26, 1918). 



The existence of definite relations of quantity of flie neurone and 

 its parts to the weiglit of the body is no longer open to doubf. ') 

 Foi- honioneuric species of mammals (species with the same organi- 

 zation of nervous svsteui), whose body weigitts are to each other 

 in the ratio of F:i, the volume of homologous neurones — as the 

 volume (or the weight) of the brain - — varies j)roportionally to P^-'»''; 

 the volume of their central |)art, the cell body proportionally to po-28. 

 It may be assumed that the ideal values are /^" ■■'•">• and /^-stt..^ 



These relations can best be verified by a study of the peripheral 

 nerve fiber. As tliis constitutes by far the greater part of the neurone 

 to which it belongs, also the volume of the homologous perii)heral 

 nerve fibers varies pretty accurately pro|)Oi'tionally to P'^-^^ for honio- 

 neuric species. And given that the length of the nerve fiber, for 

 perfecthi aniform honioneuric species, must vary proportionally to the 

 longitudinal dimension of the animal, i.e. to P^'^'^, the conclusion 

 follows naturally that both, the area of the section and the length 

 of the homologous peripheral nerves of honioneuric species, which 

 in reality — for physiological reasons — cannot be perfectly U7ii form, 

 varies about proportionally to the longitudinal dimension of the animal. 



For perfect uniformity, the area of the section would have to 

 increase proportionally to /-•«^•^^e.. j^,,j ti,e volume proportionally to /^ 

 when the nerve length increases proportionally to P^^'-^^- This now, 

 is physiologically impossible, as may appear in what follo\v8. The 

 available numerical data, considered physiologically, really lead to 

 the conclusion that the length and the area of the section of a nerve 

 increase uniforndy, i. e. botii })roportionally to po-28^ hence in the 

 same ratio as the cell-body becomes more voluminous. This holds 

 both for the neurones with peripheral nerve fibers, which conduct 

 the influxions centripetally, the sensitive nerve fibers, and for the 

 neurones with peripheral nerve fibers, through which influxions are 



1) These Proceedings. Vol. XX. (1918). p. 1328-13^7. 



