1332 



the type of tlieir species (body weights and othei- data to form an 

 opinion about this were inostiv wanting). 



Where tiie aim was merely to show that in general the size of 

 the nerve cells increases with that of the animal, the resnlts at dis- 

 posal were snflieienl. But the usefulness of the available data for 

 an enqniry into a possible regular i-elation gets very limited in this way. 



The spinal ganglion cells ai-e the most suitable for measurements, for 

 they are fairly round, and have few if any dendritic processes '). 

 But at corresponding places in the spinal cord, also the cells from 

 the coluinnae anteriores can be compared with sufficient accuracy, 

 as is particularly the case with Hakdi'.sty's measurements. On the 

 other hand the pyramidal cells of the cortex of (he cerebi-um and 

 also the Purkinje cells of the cerel^llnm can only be compared for 

 closely related animals, in which case alone we can be sure, also 

 in view of the partly undefined line of demarcation of these cells, 

 that w^e compare really homologous cells, at least corresponding 

 dimensions. G. Lkvi ') demonstrated that only of the largest cells of 

 each kind the dimensions clearly increase with the size of the body. For 

 the small cells — in this way 1 think Levi was justified in 

 accounting for this fact — the cell-body possesses less defined limits 

 that admit of measurement; a gi-eat deal of its substance (for large 

 animals disproportioually more than foi' small ones) evades observation, 

 and what is measured as such is only part of the functionating 

 cell centre. 



In the same way as foi- the quantity of biain, an exi)Ouent of 

 relation r can be calculated between the volume of the nerve cell- 

 body and that of the animal by comparison of a large species and an 

 if possible closely related small one, but \vith very large differences 

 of bodily size,' for so far as spinal cells and cells of spinal ganglia are 

 concerned, also of animals of more distant relationship. Then r is 



fo 



uud from the formula f - ) = -, in which S and ,s and G and (/ 



V « y 9 



represent the body weights and the volumes of the nerve cell-bodies 

 of the large and the small animal. 



In the following table of the most accurate available data the 

 letters placed between parentheses, behind the values in every 

 column, denote where the data are derived from. ') 



1) Compare: G. Levi, loc cit. (a), p 342—343. 



>i Loc. cit (a), p. 330, 333. 



s) (Ha): Hardksty, 1. c. p. 159— 162 and 171— 173; (DH): Donaldson and Hoke 

 1. c. p. 9 -11 ; (L) : Levi, 1. c. a. p. 331-332 ; (Addi : \V. H. F. Addison, The Develop- 

 ment of the Purkinje Cells and of the Cortical Layers in the Cerebellum of the 



