GASSERIAN GANGLION: ALBINO RAT 



249 



81 per cent of the larger in body weight, but the diameters of 

 the fibers for the smaller rats, taken from the first branch, have 

 94 per cent; from the second and from the third branches, 95 

 per cent, and from the fifth nerve, 92 per cent — thus ranging 

 from 92 to 95 per cent. 



If the observations are limited to young animals up to sixty-six 

 days in age, we find in twelve groups the relations shown in 

 table 12. 



The comparison between tables 11 and 12 shows that the 

 difference of the body weights given by the smaller and larger 

 is about the same in both tables, and in the younger rats the 

 relative size of the fibers is similar to that found for all ages 



TABLE 12 

 Average values for the diameters of the fibers obtained from young animals of different 



body weights 



Larger rats. 

 Smaller rats 

 Percentage. . 



FIFTH NERVE 



9.93 

 9.13 

 91 



combined. In general, therefore, the body weight influences 

 the size of the nerve fiber not only in the younger, but also in 

 the more advanced phase of growth. 



We consequently conclude that dissimilar body weights at 

 the same age can influence slightly more the growth of the nerve 

 fibers than that of the ganglion cells, but even in the case of the 

 fibers, where the influence is more marked, the response is 

 relatively sUght. 



THE RELATIVE SIZE OF THE SHEATH AND OF THE AXIS CYLINDER 



For this determination thirty-eight rats were used. These 

 were grouped according to the body weights, and the results 

 are given in table 13. The areas of the cross-section of the nerve 

 fibers were found by the usual formula. For each division the 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 32, NO. 2 



