1 10 'Journal of Comparative Neurology and Psychology. 



pathetic fibers enter the ganghon and break up about the cells, 

 especially those of Dogiel's Type II. The single processes of 

 these cells of Dogiel break up within the ganglion into a multi- 

 tude of little twigs which form baskets about still other cells, while 

 the stem process of many of the latter, i. e., the ordinary spinal 

 ganglion cells, gives off delicate collaterals, which also take part 

 in the formation of the fiber complex of the ganglion. All 

 this wealth of axonic ramifications, together with the dendritic 

 branches of some of the cells, forms a basis of intercommuni- 

 cation which argues for a close functional relationship among the 

 individual spinal ganglion cells. 



THE DORSAL ROOTS. 



I. The relation of the fibers of the dorsal roots to the cells in the 

 substantia grisea of the spinal cord. Examination of ^ISSh's view 

 that they are axons of such cells. — A very peculiar observation noted 

 in a paper recently published on "Retrograde Degeneration'^ 

 (Ranson 'o6), namely, that after half of the spinal ganglion cells 

 have disappeared as the result of section of the associated nerve, 

 there are to be found in the dorsal root very nearly if not quite the 

 normal number of fibers — and all this according to careful counts 

 made on a considerable number of animals — -has led to a careful 

 consideration of Nissl's ('03) recently published conception of the 

 dorsal roots, as a possible though improbable explanation of these 

 results. Had the idea that the dorsal root fibers are independent 

 of the spinal ganglion cells been advocated by any lesser author- 

 ity we might indeed pass it by as unthinkable; but we cannot so 

 lightly treat a statement by Franz Nissl. According to him 

 ('03, p. 334), "The posterior root fibers are united with the cells of 

 the spinal cord and especially with the cells of the substantia 

 gelatinosa and only pass through the ganglion; and .... the 

 cells of the spinal ganglion also send fibers toward the periphery." 

 The facts on which he bases this remarkable assertion are that 

 after section of the posterior roots the cells of the spinal ganglia do 

 not show change, while certain cells in the spinal cord, especially 

 the cells of the substantia gelatinosa, undergo chromatolysis and 

 even complete degeneration. It may be said however that, while 

 true axonal reaction does not occur after section of the root, 

 yet very considerable changes are induced in the ganglion cells 



