58 BRISTOL. [Vol. XV. 



the ganglion; therefore, near the "median" cells. In each 

 intermuscular nerve ring are about twenty-two "large bipolar" 

 cells, some of which send processes into the ganglion in the 

 neighborhood of the "median" cells, while the eight "connec- 

 tive " bipolar cells joining the two rings terminate in some 

 manner in close proximity to the fibers of the nerve ring at 

 their junction with the ring. This leaves but one " large " cell 

 yet to be accounted for, the " Leydig's cell" near the ganglion. 

 This is a bipolar cell, and the processes may be readily 

 distinguished as they pass outward on each lateral nerve totvafd 

 the periphery. These processes, however, soon fuse with the 

 nerve trunks, and I have not been able to follow them to any 

 considerable distance. It is quite significant that these same 

 trunks, or branches from them, send fibers into the intermuscu- 

 lar nerve ring, and furnish a path by which the processes of 

 this cell may reach to the other large cells. If it does not come 

 into proximity with the others, it forms an exception to all the 

 other " large " cells in the somite. 



Another fact to be noted of all these cells, numbering nearly 

 fifty in each somite, is that the nuclei are practically the same 

 in size and character, and the volume of the different cells is, 

 so far as sections show, practically the same, whatever the 

 shape may be. Such a definite arrangement cannot be without 

 a purpose, the significance of which may in some measure be 

 revealed by their development, and this I hope to determine soon. 



In brief, if by some means we could remove all other cells 

 and tissues in a somite excepting the "large" nerve cells and 

 leave them in their normal relations, we should find them all 

 joined together, forming a closed system capable, on the one 

 hand, of receiving impressions and stimulating muscles inde- 

 pendently, and, on the other hand, so related to the central 

 nervous system through the cells in the ganglia and connectives 

 as to make it completely adjunct to it. 



The Sympathetic System. 



Leydig (i8) and others have found evidences of a sympathetic 

 system arising from the collar in certain leeches and other 



1' F. Leydig: Tafeln zur vergleichenden Anatomie. Tubingen. 1S64. 



