32 S. HATAI 



therefore represent practically all salts present in the osseous 

 system. Thus in as much as the fixed salts represent practically 

 all bone ash, we should anticipate an increase of this fraction 

 from birth onwards. This appears to be the case. 



5. The composition of the entire body of various mammals at different 



ages 



It should be recalled that the protein substance given by 

 most other investigators is equivalent to the weight of 'nitro- 

 gen X 6.25.' Since the organic extractives in the present in- 

 vestigation are mainly nitrogenous substances, the residue in 

 the present case and the protein substance as determined by 

 other methods should not theoretically agree, the latter being 

 somewhat high. As to the fat, most investigators designate 

 alcohol and ether extracts collectively as fat, while the fat in 

 the present case in represented by the alcohol-ether extractives 

 minus organic extractives and salts. Thus the two data should 

 not theoretically agree. To meet the difficulties just mentioned, 

 and also to make as nearly similar as possible the two sets of data, 

 the organic extractives were added to the residue and to the 

 fat in the proportions of two to the residue and one to the fat. 

 This correction is however open to further modifications. For- 

 tunately however only comparatively small quantities of the 

 organic extractives and salts are extracted by the alcohol and 

 ether and thus the two kinds of data, our own and those from 

 the literature, may be compared directly for the purpose of a 

 rough determination. I have however adopted these corrected 

 values where the present results on the rats were compared with 

 the data given by the other investigators on various animals 

 (table 7). 



I now wish to compare the analysis of the rats with the analy- 

 ses of several mammals as recorded by other investigators. 



With the exception of those for the rat, the data which are 

 given in this table have been obtained from papers published 

 at various times by several different investigators (Aron '15). 

 It must be remembered therefore that the data are highly hetero- 



