721 



Levi the Cat has also larger ganglion cells in the coluinnae anteriores 

 of the intutnescentia lumbalis of the spinal cord than the Fox, and 

 of all the Mammals examined by him, among which the Ox, the 

 largest pyramid cells in the cerebral cortex ^). It has appeared, from 

 particularly comparable measurements of Hardesty, that the mean 

 diameter of homologous cells of the intumescentia cervicalis in the 

 Cat is not much smaller than in the Foxhound, which is 6 times 

 heavier (53.5 micra as against 58.7 micra) *). The muscle fibers in 

 the rectus femoris were thicker in the Cat than in any other Mam- 

 mal . that Levi examined, with the exception only of the Horse; 

 while the mean diameter in the Cat amounted to 55 micra, he 

 found it only 36.2 micra in a dog of about twice the weight (of 6.3 kg.) '). 



It appears, therefore, very clearly that the quick muscles of the 

 Cat's leg receive rapid impulsions from large ganglion cells through 

 thick nerve fibers. 



Something similar holds for the mole-footed Dachshund. Still 

 somewhat more rapidly than in the nervus ischiadicus of a 9 times 

 heavier butcher's dog "von der Grosse einer Deutschen Dogge" did 

 the impulsions propagate in this nerve of a dachshund (at a rate of 

 88 meters a second as against 85 meters for the butcher's dog). 



From the rate of conduction (given by Münnich) of the influxion 

 of 61 meters a second in the nervus ischiadicus of the mongrel dog 

 of the size of a foxterrier and 85 meters a second for the butcher's 

 dog, likewise of a mixed breed, which had the size of a German 

 Boarhound, and must therefore have had about 8 times the weight 

 of the smaller dog of the same species, an interindividual exponent 

 of relation for the rate at which the influxions are conducted in 

 the nervus ischiadicus of 0,1595 can be calculated. This is in 

 satisfactory agreement with the exponent 0.1344 derived above from 

 a record by Lapicque for the area of section of the eye-ball within 

 the species Canis familiaris, and the deviations from the value 

 0.28 are so great, as to justify for both cases the conclusion that 

 here the same relation of the homoneuric species is not valid, but 

 the other relation, the interindividual, which is expressed by an 

 exponent of half the value of that of the species. It does, however, 

 not follow from this that the area of the section of the nerve fiber 

 varies in the same ratio as that of the retinal area, for as the 



Italiano di Anatomia e di Embriologia. Firenze 1908, p. 177, and: Studisulla gran- 

 dezza dells cellule. I. Ibid. Vol. V. Firenze lilü6, p. 332. 



1) Ibid. (ly06), p. 834 and 337. Cf. also: K. Brodmann, Vergleichende Lokali- 

 sationslehre der Groi^shirnrinde. Leipzig 1909, p. 81. 



2; Journal of Comp. Neurology. Philadelphia 1902. Vol. 12, N». 2. p. 160. 



») Loc. cit., (190Ü), p. 827. 



47 

 Proceedings Royal Acad. Amsterdam, Vol. XXI. 



