THE NERVOUS SYSTEM. 421 



prepontlerance of unipolar, rarely of bipolar cells, differing, however, in 

 this respect, that apolar cells certainly exist in them in more consider- 

 able quantity, and the ganglion fibres arising in them are invariably of 

 the finest kind, occurring in the peripheral nerves, and probably in most 

 cases, quit the ganglia in various directions. As for a topographical 

 tracing of the various fibres in the main trunk of the sympathetic, with 

 reference to their origin from particular rami communicantes and 

 ganglia, and their continuation into particular peripheral branches, — 

 if more be required than what has already been stated — it is not by any 

 means at present to be thought of, but must be reserved for future in- 

 vestigation. 



It has been asserted, that the smaller cells in the ganglia of the 

 sympathetic are different from the larger cells in the spinal ganglia, for 

 instance ; and also that they are connected only with fine nerve-tubes 

 (Robin), but this is not correct, as is apparent in part from the observa- 

 tions of Wagner and Stannius ; for we find: 1, in the ganglia of the 

 cerebral and spinal nerves of the Mammalia and of man, all intermediate 

 sizes between larger and smaller nerve-cells, and also, occasionally, 

 though rarely, larger cells, measuring as much as 0"03 of a line in the 

 sympathetic ganglia ; and we may also be convinced, 2, that the diame- 

 ter of the nerve-fibres originating in the first-named ganglia, is not at 

 all regulated by that of the cells, all their ganglion-fibres being pretty 

 nearly of the same size, and which is confirmed also by the bipolar cells 

 of Fishes, where the one fibre arising from the cell is often considerably 

 thicker than the other ; in Petromyzon, according to Stannius, even 

 six times. Should it be at all supposed that the small cells are peculiar 

 to the sympathetic nerve alone, I must, as above, with respect to the 

 nerve-fibres, remark, that not to mention the ganglia of the roots of the 

 cerebral and spinal nerves, small nerve-cells also occur in situations 

 ■where there can be no question about the sympathetic, as in the spinal 

 cord and brain, and, — if instances of the same kind in the peripheral 

 nerves be desired — in the retina and cocJdea. At all events, this much is 

 certain, that the ganglia of the ganglionic system of nerves constantly 

 present smaller nerve-cells, and that the fibres arising from them are 

 of the fine kind only. 



Bidder and Volkmann have shown, in the Frog, that the greater part 

 of the fibres of the rami communicantes are distributed peripherally, 

 with the spinal nerves, and that only a small portion of them, which 

 moreover are derived from the spinal ganglia, should be regarded as 

 roots of the sympathetic. But I think I have noticed in the Rabbit 

 and in Man, that the rami communicantes have chiefly a central des- 

 tination. Still, in man, fibres also occur very frequently — according to 

 Luschka always, — which must be regarded as branches of the sympa- 



