114 SHINKISHI HATAI 



however, animals lower in the zoological scale are taken, Type 

 1 tends to resemble Type 2. 



This can be seen from the graphs for the growth of the brain 

 weight in the fish (Kellicott '08) and in the frog (Donaldson 

 '03). Type 3, however, seems to be quite characteristically 

 differentiated from the rest even in the fish, as shown by the 

 graph for the gonads. The relative growth of the organs i-ep- 

 resented by these three types of graphs is represented in table 3. 



The data giving the percentage growth of the brain and spinal 

 cord (Donaldson '08) are included for comparison. In the case of 

 each organ in table 3 the percentages were calculated by taking 

 the final weight of the organ, at a body weight of 450 grams for 

 the male, as 100 and then expressing the preceding weights as 

 percentages. In the case of the female, the final organ weight 

 (100) was taken from the rats of 300 grams in body weight. This 

 is about the average maximum body weight the female can 

 attain. 



Examination of table 3 reveals many interesting points. First 

 of all the three types of growth are clearly shown; that is the 

 eyeballs and the nervous system are characterized by a precocious 

 growth in an earlier stage. Fifty per cent of the final weight is 

 attained by the brain in rats when still below 20 grams in body 

 weight — in the case of the spinal cord, below 100 grams and in 

 the case of the eyeballs, below 130 grams. In the viscera and 

 ductless glands on the other hand, 50 per cent is attained at a 

 body weight of about 200 grams or more. In the case of the 

 sex glands, half of the final weight is attained at about the same 

 stage as the eyeballs 130 grams. Nevertheless the characteris- 

 tic double or triple phases of growth serve to distinguish clearly 

 the type of the gonads from that of the eyeballs or nervous 

 system. 



It is highly interesting to notice the similarity of growth rate 

 of all the abdominal and thoracic viscera and ductless glands, 

 especially after the 50 per cent increment has been attained. 



This similarity of the growth rate of the organs just named 

 throughout this first third of the span of life suggests a close 

 quantitative interrelation between these various organs and their 



