82 ELBERT CLARK 



eration failed to take place in those meduUated fibers showing 

 the most marked degeneration; and that in its recovery the fowl 

 gradually learned to do without these fibers. Further study 

 convinced me, however, that this was not the case, and that 

 those fibers which had shown such marked degeneration finallj" 

 attained a new axis cylinder. This conclusion became evident 

 after a close study of the axis cylinder in those fowls which had 

 recovered from paralysis. 



Mallory's phosphomolybdic acid hematoxylin, carmine, Cajal's 

 new silver impregnation method for axis cylinders, and Hanson's 

 modification of the last were used for staining the axis cylinder. 

 The preliminary treatment (i.e., hardening in absolute alcohol) 

 called for in the silver methods produced such shrinkage of the 

 fibers that it was often impossible to obtain satisfactory teased 

 preparations. The degenerated myelin was also dissolved out 

 to such an extent, that together with the shrinkage, relations 

 were so distorted that it was usually difficult to distinguish an 

 old from a new axis cylinder and to tell the relation of the latter 

 to the globules of myelin. With the first two methods it was 

 possible to stain a preparation in bulk, clear and tease out with- 

 out passing through the higher alcohols or xylol. The globules 

 of degenerated myelin were thus preserved. With the phospho- 

 molybdic acid hematoxylin, which gave beautiful results after 

 proper fixation with Miiller's fluid, the procedure was as follows: 

 Fix in Miiller's fluid (small pieces as fresh as possible), wash 1 

 to 2 hours in running water, partially tease out a segment of the 

 nerve not more than 1 mm. long to permit rapid infiltration of 

 the stain, place in a ripened solution of Mallory's phosphomo- 

 lybdic acid hematoxylin 20 minutes to over night, blot off excess 

 of stain and differentiate in 50 per cent alcohol made slightly 

 alkaline with ammonia, pass through two or three changes of 91 

 per cent alcohol, clear in origanum oil, tease, blot, and mount 

 in xylol balsam. Carmine preparations were prepared in a simi- 

 lar manner but differentiated in weak alcohol without the ammo- 

 nia. For longitudinal and cross sections, pieces of nerve after 

 washing were rapidly dehydrated and cleared and mounted in 

 paraffin and stained as indicated. Tissues were also fixed in 



