504 



M. J. GREENMAN 



Donaldson and Hoke ('05) in an examination of the nerve 

 fibers from a large series of vertebrates which included the albino 

 rat, found -the area relation of axis to sheath to be approximately 

 as one to one. The results here given are in substantial agree- 

 ment with their observations. 



Dunn ('12) found in the albino rat that medullated nerve 

 fibers and their axis cylinders increase continuously in size until 

 270 days of age and that in old rats, about 640 days of age, 

 there is a noticeable decrease in size of both the nerve fiber and 

 its axis cylinder. Dr. Dunn also followed the changes in the 

 axis sheath relations with age. 



AXIS-SHEATH AREA RELATION: OPERATED ANIMALS 



Passing to the consideration of the axis-sheath area relation 

 in operated animals, we observe from table 10 that the percent- 

 age of axis in operated animals is less than in normal animals., 

 The average percentage value of the axis in the largest fibers of 

 the controls shown in group 1 (nos. 106, 114 and 154) is 44.1 

 per cent. The sheath, therefore, constitutes 55.9 per cent, but 

 it should be recalled that these fibers in the control nerve have 

 suffered a diminution in total area of 42 per cent as the result 

 of the operation. 



If we take from table 10 the average percentage value of the 

 axis, and compute the sheath value, (1) of the controls and (2) 

 of the proximal, and (3) distal ends of the operated nerves in the 

 first four groups, and then arrange these values under their proper 

 headings, we get table 12. 



