Johnston, Giant Ganglion Cells. 377 



nated in these preparations and the tracts can usually be iden- 

 tified with perfect certainty in any given preparation by means 

 of the central processes of the spinal ganglion cells (Figs. 4, 5, 

 6, 7). The rostral neurites are slightly coarser than the fibers 

 of the dorsal tracts, sometimes much coarser. They can be 

 traced forward for a considerable distance in most preparations 

 before being lost among the dorsal tract fibers. In a few cases 

 I have traced these fibers with certainty to the cephalic end of 

 the cord (Fig. 3) and in one case (Fig. 2 A) have found the 

 fiber breaking up into a number of branches in the nucleus 

 funiculi. In the same individual two cells situated in the caudal 

 part of the medulla send their neurites forward in the spinal V 

 tract toward the tuberculum acusticum. The latter body is 

 identified by the entrance and end-branching of the fibers of 

 the lateral line VII nerve (Fig. 2 A). In many cases the rostral 

 neurites bear small lateral twigs and longer branches similar to 

 those seen on the fibers of the dorsal tracts. 



The caudally directed neurite arises usually from some part 

 of the dendrite, occasionally from the cell body, and rarely by 

 T-division of a single neurite (Fig. 6 B). It also runs among 

 the fibers of the dorsal tracts. The fiber is more slender than 

 either the rostral neurite or the fibers of the dorsal tracts. It 

 frequently shows divisions early in its course (Fig. 2) and is not 

 so long as the rostral neurite. 



There are a few exceptional cases in which the dendrites 

 go to the opposite side of the body from that on which the cell 

 lies, but the neurites never cross to the opposite side. 



In Coregonus albus the number of cells is very much less 

 than in Catostomus, but my histological sections are not satis- 

 factory for counting the entire number in any one specimen. 

 The number is probably between forty and fifty. The only 

 other difference between these elements in Coregonus and 

 Catostomus lies in the fact that in Coregonus the dendrite is 

 directed rostrally and the rostral neurite arises from the den- 

 drite, while the caudal neurite arises from the cell body or from 

 the dendrite (Figs. 8, 9). 



The interpretation of these cells seems to be not difficult. 



