264 KENJI NITTONO 



observations on other spinal ganglia and on the ganglia of the 

 several cranial nerves are needed before any general conclusions 

 can be drawn, but if we use the present observations and take 

 the seventh cervical ganglion as the standard, it appears that 

 the gasserian ganglion is characterized by larger cells, smaller 

 nuclei, and a higher nucleus-plasma ratio, while the fibers form- 

 ing the sensory root are smaller, though the axis sheath relation 

 is the same in both. 



When growth after 80 grams of body weight, i.e., after puberty, 

 is considered, it appears that the growth of the cells comes nearly 

 to a standstill at puberty, though the fibers continue to increase 

 in diameter to a slight extent. 



It seems possible from these relations that the neurons in the 

 more specialized cranial ganglia mature earlier than do those 

 in the spinal ganglia. 



SUMMARY 



The measurements were made on twenty-five of the largest 

 ganglion cells in seventy-six gasserian ganglia taken from thirty- 

 eight normal albino rats, and on the ten largest fibers from the 

 first, the second, the third branch, and the fifth nerve root in 

 thirty-nine albino rats. 



For the fixation of the cells Bouin's fluid was used, and for the 

 fibers one per cent osmic acid. 



From these data the following results were obtained : 



1 . The growth of the ganglion cells shows three distinct phases : 

 1) a rapid growing period which extends from birth to about 

 20 days; 2) a slower growing period which covers from about 

 20 to about 80 to 100 days; 3) finally, a period of much slower 

 rate (or even a slight atrophy) which extends to the end of the 

 observations, or 485 days. The growth of the nucleus shows 

 phases similar to those for the cell bodies. 



2. The nuclei are relatively well developed at birth and their 

 increase in diameter is slower than that of the cell body. 



3. Among rats of the same age those with heavier body weights 

 have larger cell bodies, nuclei, and fibers than those which are 

 smaller. This influence of the body weight on these structures 



