R ANSON, A If ('rations in Spinal Ganglion Cells. 127 



to be answered, however, before any solntion of the problems, already 

 mentioned, could be reached; and, accordingly, the prime purpose 

 of the present investigation is to follow the various stages of axonal 

 reaction in sections, prepared for that purpose, in order to determine 

 whether it is chiefly the large or the small cells which undergo 

 complete disintegration. 



ISTaturally, there were also other problems which engaged the 

 attention as the investigation progressed. The more important of 

 these can be stated briefly as follows : 



1. Can the cells of Dogiel's Type II, or his new types III, IV, 

 VIII, and XI, which send no axon into the nerve, be identified by 

 their failure to show chromatolysis after the section of the periph- 

 eral nerve ? 



2. What proportion of the spinal ganglion cells react to the 

 section of the nerve ? When it is remembered that there are on the 

 average three spinal ganglion cells for each medullated afferent 

 fiber in the nerve, and that most observers have foimd nearly all 

 the cells showing the axonal reaction, this question becomes a very 

 pertinent one. 



3. If all the cells react, is there any indication that the reaction 

 in some is secondary to that in others ? That is to say, do the small 

 cells, which do not have medullated axons in the nerve, react so 

 much later than the large cells that one might interpret their altera- 

 tions as due to a j^urely intra-ganglionic disturbance ? 



4. What is the nature of the degenerative processes which, as 

 has been shown, lead to the disappearance of about half the cells ? 



5. Is there any special locality in the ganglion where the cell 

 destruction is most marked, or any part which remains intact ? 



6. Can the cells wdiich survive be followed through the stages 

 of repair until they are again of normal appearance ? .If so what 

 type of cell is most likely to undergo repair ? 



Technique. 



The second cervicail nerve of the right side was cut under aseptic 

 precautions in white rats 12 days old. The technique of the opera- 

 tion was the same as that described in the paper on "Retrograde 



