508 NAOKI SUGITA 



the diameters which is thus brought about tends, as a mere mat- 

 ter of arithmetic, to make the values of their product less than 

 it would have been had their proportions remain the unaltered. 



Sex characteristics. When brains of different sexes but of like 

 weight were compared, there was not detected any considerable 

 sex-differences in measurements, except in three cases. These 

 individuals had apparently an elongated form of brain, their 

 lengths being markedly high as compared with the average 

 values for the brains of like weight. These three were all old 

 females, exact age unknown. ^ In other respects, even these 

 brains, showed no peculiar characteristics. 



Hatai ('07) concluded from his skull measurements of the 

 mature albino rats that, in every respect other than the nasal 

 bone, the female cranium might be considered as an undersized 

 male cranium, and vice versa, since the other differences found 

 between the two sexes were too small to be significant. This 

 statement is probably true for the form of the cranial cavity, 

 i.e., the form of the brain, as indicated by my measurements on 

 brains of like weight but different sex. According to Hatai 

 ('07) the skull capacity of the mature albino rat measured and 

 represented by shot weight, is thus; male: 10.896 grams, female: 

 10.368 grams, which empirically correspond to the brains weigh- 

 ing 1.822 grams (male) and 1.725 grams (female) respectively, 

 suggesting that the specific gravity of the male brain substance 

 is slightly higher than that of the female (male 6.009: female 

 5.980). 



VI. SUMMARY 



1. On the fresh brain of the albino rat, five diameters were 

 measured at fixed localities. By these the shape and the size 

 of the cerebrum can be indicated and by the changes in them, 

 the postnatal growth can be studied. As material 141 albino 

 rats at every stage of growth were used. 



^ According to my observations, the brains from rats which were severely 

 underfed for a long time and whose body weights were reduced considerably, in 

 the younger age, not only weigh less than the brains of standard rats of like age, 

 but have generally an elongated shape as compared with the controls. 



