496 



NAOKI SUGITA 



on a small number of cases, the following may be reported. In 

 table 1 are given for ten ages the total brain weights and their 

 ratios, the weights of the parts and the ratios of the weights of 

 parts to their respective initial weights at birth. It is seen from 

 these data that throughout the early period of life (first 150 days), 

 the cerebellum develops most rapidly, the olfactory bulbs show 

 the next highest rate, while the stem develops rather steadily 



TABLE 1 



Giving for ten ages the total brain weights and their ratios, the weights of the parts 

 and the ratios of the weights of parts to their respective initial weights at birth, 

 albino rat brain 



1 The olfactory bulbs are very variable in weight. Undeveloped bulbs like 

 the above sometimes occur. 



during that period. The cerebrum, however, develops in a ratio 

 equal to that of the entire brain, from which fact we may con- 

 clude that the developmental stage of the cerebrum is fairly 

 represented by that of the entire brain. 



This preliminary examination was made to ascertain whether 

 or not the developmental weight phases of the cerebrum are 

 represented by those of the total brain weight. It appears that 

 they are thus represented, so that total brain weights may be 

 used when cerebrum weights are not available. 



To study the developmental changes in the shape and size of 

 the cerebrum, I selected five diameters of the entire cerebrum. 



