TISSUES OF THE BODY. 



313 



ganglion cells are also of frequent occurrence here. Nor dare we form 

 conclusions in regard to the mammal body from what is found in the fish. 



The existence, however, of apolar, unipolar, and bipolar ganglion cells, 

 cannot be denied in this case 

 also after candid consideration, 

 although we are still in the dark 

 as to the relative frequency of the 

 various forms. 



Multipolar cells must be looked 

 upon as peculiar to many peripheral 

 ganglionic masses, as also to the 

 terminal expansion of the optic 

 nerve in the retina. They were 

 discovered by Remak in the sym- 

 pathetic. 



The same species of, and pos- 

 sibly also exclusively, multipolar 

 ganglion cells, occur likewise in 

 the grey matter of the brain and 

 spinal cord (fig. 305); those apolar 

 specimens which are found here, 

 or such as have only one or two 

 processes, being probably mutilated 

 cells ( Wagner, Schroder van der 

 Kolk). These cells, which contain 

 either a pale substance alone (2), 

 or, besides this, brown and black 

 pigmentary particles (4), possess a 

 very variable number of ramifica- 

 tions, ranging from 4 to 20 and 

 upwards (1-4). The latter appear, 

 under high magnifying power, 

 partly as broad or narrow processes 

 of the finely granular cell body 

 (2, c), and partly homogeneous 

 (1, a). Some of these ramifica- 

 tions split up eventually, with 

 repeated subdivision (4), into fibres 

 D extreme fineness. Others, acting 

 is commissures (2, c; 3, b), are sup- 

 posed to combine the ganglion 

 cells to a physiological unit (4). 

 Finally, axis cylinders are seen 

 arising from them (fig. 305, 1, a, 

 b; 3, c; and 298, </*). 



It is at present impossible to trace any connection between the variation 

 in the ganglion cells just described, and a difference in function in each or 

 any. 



REMARKS. 1. In older historical works of the year 40, apolar ganglion cells 

 alone were recognised. Purkinje, it is true, had seen the processes of ganglion cells in 

 1 838, but had not recognised their significance. Subsequently toHelmholtzs and Will's 

 discovery of the one-sided origin of fibres among the invertebrate animals, Koelliker, 

 was the first to demonstrate its occurrence among the vertebrates. Great progress was 

 next rn^de in this direction in the year 1847, through the discovery, by Wagner and 



Fig. 304. Xerve cells from the peripheral ganglia 

 of Gaduslota. a, b, c, Bipolar connected with 

 broad nerve fibres ; d, similar cell produced into 

 a narrow fibre ; e, another of the same kind, from 

 which a nerve fibre has been torn off; /, an uni- 

 polar cell with narrow tube; g, two bipolar (g-l, 

 g-2) peculiarly united to fine nerve tubes; h, an- 

 other bipolar cell ; t, k, two apolar ganglion cells. 



