116 SHINKISHI HATAI 



relative independence of both the gonads and the nervous sys- 

 tem. A direct comparison between the two sexes with respect 

 to the relative growth rate, as here given, cannot be made because 

 the final body weight taken in the case of the female is different 

 from that taken for the male. Nevertheless a study of both 

 table 3 and the charts shows that both the ductless glands and 

 the ovary grow in the same manner as the corresponding organs 

 in the male. 



GENERAL CONSIDERATIONS 



The usual view that the viscera are highly variable, in man 

 for example, seems to have arisen largely (1) from the use of in- 

 dividuals past the prime of life, that is, more than thirty years 

 of age; (2) from confusing normal and pathological material, 

 and (3) from treating the data without proper regard for the 

 controlling factors of race, age, body weight, stature and sex. 

 Indeed from a standpoint of curve fitting the viscera are prob- 

 ably no more variable than other parts of the body. 



This optimistic view is based on the data presented in this 

 paper. It will be noticed that the total number of rats used is 

 certainly not large, when the range of body weight is considered. 

 Nevertheless, the resulting data show a considerable uniformity 

 and the observed values do not usually deviate to any great extent 

 from those calculated. 



It should be possible, however, to get even a better agreement 

 between the observed and computed values for the albino rat 

 were it possible to control certain important modifying conditions. 

 What these conditions are may be briefly stated. 



Factors modifying the relative weights of the organs 



1. Food, care and physical condition of rats. It is generally 

 assumed that the rat can eat anything and can grow and multiply 

 under almost any conditions. It is true that one can raise rats 

 with an ordinary bread and milk diet, or e\ en with some arti- 

 ficial diet, for one or. two generations if the original strain was 

 thoroughly sound. 



