720 



that they have a real meaning. In this connection the much smaller 

 deviation found b}' Alcock between tall and short men, does not 

 even seem to be entirely devoid of interest, now that it appears 

 to rnn parallel with that between the dogs of a much more conside- 

 rable ditïerence of weight, and these results are in accordance with 

 what was forced on our attention about the significance of the 

 dimensions of the nerves. 



For a dog, "brauner Bastard von der Grosse eines Fox terriers," 

 Avhich must have weighed about 7 or 8 kg., Münnich tinds a i-ate 

 of 61 in. [)er second, equal to that for the Rabbit, which can only 

 [lave had about one fourth of this body weight. Hence the rapidity for 

 the Rabbit is comparatively great, and we accordingly tind for this 

 burrowing Rodent thicker nerve tibers than for the Dog. As mean 

 diameter in the plexus brachialis Donaldson and Hokk found 13.3 

 micra for a Rabbit and 11.6 mici'a for a She|»herd's Dog (probably 

 8 times heavier). A definite ratio between the rapidity and the area 

 of the section can, however, not be derived tVom this, because 

 different nerves and difllerent bi'eeds of dogs are compared here. 



For his largest cat Münnich found a rate of 81 meters per second, 

 for another specimen, of which he feels it necessary to state that 

 it is adult, and for which he experimented on a shorter length of 

 nerve, which specimen will therefore have been smaller, the rate 

 was 75 meters. As e\en the largest cat can hardly have reached 

 half the weight of a middle-sized Foxterrier, the rapidity is certainly 

 relatively very large for the Cat. Undoubtedly tiie considerable 

 thickness of the nerve fibers in the Cat is in connection with this, 

 on an average in the plexus brachialis a diameter of 16 micra, as 

 against 1J.6 micra for a dog 5 times heavier according to Donaldson 

 and Hoke. *) Besides, the Cat is also distinguished by particularly 

 large ganglion cells (a peculiarity of all the Felis species). The 

 muscle -fibers of the extremities, too, seem to be particularly thick. 

 Already Cavazzani had found that the cells of the cervical and of 

 the lumbal ganglia spinalia are particularly large, and equal to the 

 corresponding cells of dogs which are 5 times heavier*). Also Levi 

 found the cells of the fifth cervical ganglion spinale in the cat much 

 larger than in an about equally heavy dog (diameter 81 as against 

 65.6 micra). They only reached an almost equal diameter (79.7 

 micra) ') in a dog of 7 times the weight (of 23 kg.). According to 



1) Loc. cit. 



2) E. Cavazzani, Sur les ganglions spinaux. Archives Italiennes de Biologic, 

 Tome 28. Turin 1897, p. 52. Shepherd's Dogs, Pointers, and adult cat. 



s) G. Levi, 1 gangli cerebrospinali Supplemenlo al Vol. VII dell' Archivio 



