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KEN J I NITTONO 



maximum at the fifth group (189.2 grams in body weight), and 

 then remain nearly constant. On the other hand, the nuclei show 

 slighter changes in the values of ratios from birth to old age, 

 indicating a less rapid increase in size. These relations are shown 

 by the graphs in charts 1, 2, and 3. 



The ratios of the volumes of the cytoplasm to the volumes 

 of the nucleus were calculated according to the following formula : 



(DC^ - DN^) / DN^ = Ratio 

 where DC = eel) diameter, DN nucleus diameter. 



TABLE 7 



Showing the increase in the cell body and the micleus as ivell as relative size of the 



cell body and the nucleus for the increasing body weight of the 



rats — in six groups on body weight 



The data thus obtained reveal several interesting relations. 

 The ratio given by the first group (table 7) is 1.0:11.8. This, 

 however, increases very rapidly to 1.0: 18.4 for the second group, 

 but the change becomes slower up to the fifth group in which 

 the ratio is 1.0:25.7, and thereafter it remains nearly constant. 

 Thus in the earlier phases of growth the enlargement of the 

 cell body is more rapid than that of the nucleus. This process 

 goes on steadily until the ratio reaches a maximum at the 

 fourth group. The differences which exists between the last 

 three groups are too small to be considered as significant. It 

 is thus evident that during the growth of the cell body and 

 nucleus the ratio more than doubles, and this doubling occurs 

 before puberty, but after that age neither the cytoplasm nor 



