286 Journal of Comparative Neurology and Psychology. 



cepting uncritically the results of such recent researches as those of 

 Ballance and Stewart and of Bethe. 



The method relied upon chiefly was fixation and staining by vom 

 Rath's fluid, followed by pyroligneous or pyrogallic acid. The research 

 contains a number of careful drawings. It is rather to be regretted, 

 perhaps, that black and white drawings and line reproductions were 

 used. Outlines of cells and fibers are of great importance in such a 

 research and the effect of such a method of illustration must inevitably 

 be to exaggerate their definiteness as compared with the actual prep- 

 arations. 



The first neuroblasts are found to be developed not from rounded 

 "germinative" cells, but from the ordinary epithelial cells of the neural 

 tube. The neuraxone is formed before any migration takes place. 

 Xeal agrees with Dohrn, Bethe and others in asserting a migration 

 of the cells from the neural tube along the ventral root. This view 

 certainly seems to be now best supported and makes it easier to under- 

 stand the processes of histogenesis and regeneration if such views as 

 those of Ballance and Stewakt and Bethe be correct. Xeal, how- 

 ever, denies that these migrated cells take part in the formation of the 

 ventral root fibers and believes they form the neurilemma, jjossibly 

 also contributing to the connective tissue sheaths and the sympathetic. 

 The migration of the cells is shown by the presence of cells half in 

 and half out of the medullary wall, also by their presence in the part 

 of the nerve next the neural tube. Neal is also inclined to believe 

 that mesenchyme cells contribute extensively toward the formation of 

 the neurilemma. 



These migrated cells of the ventral nerve are believed to have noth- 

 ing to do with the formation of neuraxones because they are peripheral 

 to and with their long axes perpendicular to the fibrous portion of the 

 nerve when the neuraxones are forming most rapidly, because they do not 

 exhibit the staining reactions of the cells of the dorsal ganglia, because 

 they do not undergo the characteristic changes of shape of the latter 

 and because nothing resembling a neuraxone was to be found in their 

 cytoplasm, On the other hand, the spinal ventral nerves in their 

 earliest stages of development certainly arc processes of medullary cells 

 and devoid of nuclei and the same continuity can be made out later. 

 The number of neuroblasts whose axones can be traced into the nerve 

 also corresponds with the estimated number of neuraxones in the nerve. 



These reasons bring Neal to the conclusion that the process the- 

 ory of the development of the ventral nerve fibers is the correct one. 

 Neal thus agrees with the prevailing view of His, though differing 



