EDnouiAL, Pr( bhii/s of Comparative N'citrology. 97 



The cells of the first class predominate in the dorsal 

 cornu, especially in the substantia gelatinosa of Rolando 

 and may be regarded as sensory, while the second class 'pre- 

 dominates in the ventral root zones. 



V In the gray substance there is a difluse nervous reti- 

 culum, which is also continued into the medulla and higher 

 regions. This reticulum in the spinal cord consists of the 

 following elements: [a] fibres partly from the reticulum of 

 the gelatinous substance and partly from the dorsal cornu 

 proper; (<5) nerve fibres from the dorsad roots, which sub- 

 divide in the same complicated manner as described for the 

 processes of the nerve cells; (r) fibrillce from the processes 

 just named, which retain their identity; (</) fibrillae which 

 arise from the axis cylinders of the various columns and pass 

 transversely into the gray matter and there subdivide as in 

 the other cases. 



6. In order to establish the functions of cells or cell- 

 clusters from the evidence of anatomy, one must chiefly rely 

 upon the course and relations of the nervous processes. 



7. In the gray substance of the spinal cord it is impossible 

 to give an accurate topographical description of the groups 

 of ganglion cells, because their distribution varies exceed- 

 ingly in the smallest areas; neither would such a grouping be 

 serviceable, for it does not appear that cells of the same 

 group necessarily have the same function. It, in fact, 

 frequently happens that adjacent cells send their nervous 

 processes in opposite directions. 



The following cells belong to the first class (those in 

 which the nervous process terminates in a reticulum): (a) 

 cells of the substantia gelatinosa of Rolando; {b) cells of 

 the dorsal cornu proper; (r) sporadic cells in the zone 

 between the dorsal and ventral and even within the latter. 



To the second class (those with axis cylinder processes) 

 belong the following: {a) the larger part of the cells of the 

 ventral cornua; {h) a few cells pertaining to the dorsal; 



