722 



length of the nerve fiber varies, from one individual to another within 

 a species, without change of the number of the nodes of Ranvier, 

 where the resistance for the nerve inflnxion must be much larger 

 than in the internodia, the resistance in the larger animal becomes 

 slighter in inverse ratio to the length of the nerve fiber. I imagine that 

 in this way the nerve fiber, from individual to individual within a 

 species, does not actually become thicker, only longer. This is different 

 for homoneuric species; there the number of internodia, hence also 

 of the nodes, increases in direct ratio to the lengtli of the nerve 

 fiber, which does not bring about a change in the i-apidity of the 

 intUixion (per unit of length); this is, therefore, directly dependent 

 on the area of the section. 



When the propagation of the intluxions in the nerve fiber is 

 compared with the motion of electricity in a circuit, in which the 

 resistance (the reciprocal value of the conductivity) is in inverse 

 ratio to the section, and in direct ratio to the length, much becomes 

 clear in the relations' of the size in the nervous system that would 

 otherwise remain unaccountable. Then the ganglion cell may, in a 

 certain sense, be compared with an electric condensator or storage 

 battery, which is charged and discharged. 



In the first place it becomes clear that only on comparison of 

 homoneuric species the legular quantitative relations of the neurone 

 and its parts to the body weight are found. For the exponent of 

 relation for the volume of the largest ganglion cells of the columnae 

 anteriores in tlie intumesceiitia cervicalis the value 0,2387 is found 

 between Horse and Mouse, according to Hardksty's records, the 

 value 0.3931, on the other hand, between Cat and Mouse ; the expo- 

 nent is only 0.0851 between Horse and Cat. A Cat that had the 

 weight of the Horse, would have a ganglion cell for the motor 

 nerve fiber of the claw muscles 2.763 times as voluminous as the 

 cell belonging to the longest motor nerve fiber of the Horse. 

 Hakdesty points out (p. 166) that the American Hoary Bat (Atalapha 

 cinerea Pal.), which is considerably smaller than the House Mouse, 

 possesses somewhat larger cell bodies in the columnae anteriores 

 of the intumescentia cervicalis than the latter, which he brings in 

 connection with the innervation of the wings. Obeksteiner also sees 

 a connection between this great functional importance of the fore- 

 legs as wings in the Bats and the fact that, while for most Mammals 

 the cells of the intumescentia lumbalis are appreciably larger than 

 those in the intumescentia cervicalis, the reverse is true for Bats '). 



1) H. Obkrsteiner, Bemerkungen zur Bedeutung der wechselnden Grosse von 

 Nervenzellen. (Del Volume Jubilare in onore L. Bianchi. Catania 1913), p. 4. 



