246 



KENJI NITTONO 



Those fibers belonging to the second and the third branches 

 measure 10.2 /^ and 10.2 (x, respectively, while the corresponding 

 axis cylinders measure 7.0 /x and 7.1 fx. The fibers in the last 

 two branches show, therefore, about the same diameters. 



From chart 4 we can clearly distinguish in the fibers three 

 different phases of growth such as were noted for the growth of 

 the cell bodies. Thus the diameters of all the fibers increase very 

 rapidly from the fourth day after birth up to twenty days in 



O 30 50 100 150 20'; 250 300 350 400 



Chart 4 Based on table 10, giving, on age in days, the diameters of the largest 

 entire fibers in the root and branches of the fifth cranial nerve of the albino rat. 

 R = graph for the fibers in the root; I = graph for the fibers in the R. ophthal- 

 micus; II = graph for the fibers in the R. maxillaris; III = graph for the fibers 

 in the R. mandibularis. 



age (23.4 grams in body weight), and this rapid increase becomes 

 slower until eighty to one hundred days in age (100.5 to 125 

 grams in body weight). After this the fibers, however, continue 

 to grow steadily but very shghtly throughout the period of the 

 observations. 



These results thus approximately correspond to those repre- 

 senting the growth in the diameters of the spinal ganglion cells 

 and fibers (Donaldson and Nagasaka, '18), with one difference: 

 the cell bodies in the gasserian ganghon reach a maximum at an 

 earlier period (about puberty) and then remain nearly constant. 



