118 S. WALTER RANSON 



from these small cells as well as from the cells of the zonal layer 

 and the cells of the nucleus of the columna posterior. 



It is a fact of general knowledge that the substantia gelatinosa 

 contains very few medullated fibers, with the exception of the 

 bundles of fibers from the dorsal roots and the posterior funic- 

 ulus, which run through it on their way to the more ventrally 

 placed portion of the gray substance. 



It has been known that non-medullated fibers were present in 

 abundance and Rosenzweig ('05) and Sano ('09) have recently 

 emphasized that fact. Contrary to the opinion of Weigert, 

 Rosenzweig states that neuroglia cells and fibers are present in 

 abundance. According to this author, nerve cells, axons, den- 

 drites, glia cells and glia fibers fill the substantia gelatinosa com- 

 pletely. There is no intermediate gelatinous substance in a 

 good Bielschowsky preparation, but this appears only in propor- 

 tion as poor fixation has resulted in the destruction of the proto- 

 plasmic elements. 



In pyridine-silver preparations the cells of the substantia 

 gelatinosa are not very well stained and it is often impossible to 

 distinguish between nerve cells and neuroglia. But the nerve 

 fibers are well differentiated and it seems worth while to give an 

 account of these as they are seen in the monkey cord, and to men- 

 tion such differences as are seen in other animals. 



The substantia gelatinosa presents two well-defined layers, the 

 most superficial of which has received the name of stratum zonale. 

 In the seventh cervical segment of the monkey cord this zonal 

 layer (fig. 4, S.Z.) is especially marked in relation to the apex of 

 the substantia gelatinosa, and projects as a triangular area into 

 the tract of Lissauer. And from this apical mass the layer ex- 

 tends forward as a thin covering on either side of the substantia 

 gelatinosa. In pyridine-silver preparations the stratum zonale 

 is deeply stained because of the large number of fine axons which 

 it contains. There is a constant interchange of fibers between 

 it and the tract of Lissauer, and between it and the deeper layer. 

 While the fibers run in every direction, there is a tendency for 

 them to be tangential to the surface of the substantia gelatinosa. 

 From the triangular mass at the apex numerous fibers run for- 



