1331 



which is only 127, times, and the lengtli nearlj' 2'/, times tl)at of 

 the albino mouse, the diameters of homologous nerve cells to be 

 proportional to 5 and 4. 



In order to give a preliminary idea of the order of magnitude of 

 these differences in the size of the nerve cells, may serve that in 

 general, with closely related species, a doubling of the length 

 measures of the animal is accompanied with an increase of the diameter 

 of the cell-bodies in the ratio of only 5 : 6. Given, moreover, the 

 very irregular form of many cell-bodies, it is easy to understand 

 that most neurologists did not ascribe any signification to those 

 differences in size. 



However, chiefly Irving Hardesty *), Giuseppe Levi '), H. Ober- 

 STEiNER *) have conclusively proved that the size of the cell-bodies 

 in general increases with the bodily size of the species of animals. 

 Taken as such, the data su{)plied by them, do not, howevei-, prove 

 the existence of a distinct, regular proportionality. On the contrary, 

 although the large species in most cases are very distant from the 

 small species, there are many exceptions, ihe series being in part 

 verj' irregular. For certain kinds of cell-bodies this is owing to 

 their shapes, which do not admit of accurate measurements, but 

 assuredly to a much greater extent to the circumstance that mostly 

 cells from different parts of the spinal cord are compared, though 

 the size of the cell-bodies varies greatly for the same animal according 

 to the place in this central apparatus *), further to the circuujslance 

 that there can exist specific inequality in the size of corresponding 

 cells according to the species of animal, and last not least to 

 this that the examined specimens by no means always represented 



^) Ihving Hardesty, Observations on the Medulla Spinalis of the Elephant with 

 some Comparative Studies of the Intumescentia Cervicalis and the Neurones of the 

 Golumna Anterior. Journal of Comparative Neurology. Vol. 12. Philadelphia 1902, 

 p. 125—182. 



*) a. Giuseppe Levi, Studt sulla grandezza delle cellule. 1 Ricerche comparative 

 suUa grandezza delle cellule dei mammiferi. Archivio Italiano di Anatomia e di 

 Embriologia Vol. V. Firenze 1906, p. 291—358. For all classes of Vertebrates: 

 b. G. Lkvi I Gangli Cerebrospinal!. Supplemento al Vol. 7 dell' Archivio Italiano 

 di Anatomia e di Embriologia. Firenze 1908. 



') H. Obersteiner, Bemerkungen zur Bedeulung der wechselnden Grosse von 

 Nervenzellen. (Del Volume Jubilare in onore L. BiANCHi. Catania 1913), 8 pp. 



*) We may remind here of the fact that for man, the dog, the cat, the rabbit, 

 and the rat, all adult, E. Cavazzani found on an average smaller mean 

 diameters of the cell-bodios in the ganglia spinalia between the thoracic vertebrae 

 than between the cervical and lumbar vertebrae. (Bur les ganglions spinaux. Archives 

 italiennes de Biologie. T. 28 (1897), p. 52—53). 



