25 



and if possible a roughly approximate estimate of the proportions in 

 which they severally occur ; also it is clear that the factor to be used 

 in calculating the nitrogenous constituents to be reported under each 

 analysis should be decided by such preliminary investigation. In the 

 light of present knowledge of this kind the writer is inclined to sug- 

 gest the following numbers: 



For proteids and allied substances, multiply nitrogen found by 6.25, 

 as usual at present. 



For flesh bases and simpler amids of animal origin in food mate- 

 rials, multiply by 3.05. 



For simpler amids and amido-acids of vegetable origin in food mate- 

 rials, multiply by 5.15. 



For mixed amidic constituents of unabsorbed solid residua in diges- 

 tion experiments, multiply by 9.45. 



As a matter of general practice, in all statements of the results of 

 nutrition experiments the rule should be invariably observed to give 

 the actual amounts of nitrogen obtained by analysis, whatever calcu- 

 lated conclusions be afterwards deduced therefrom ; so that, with fur- 

 ther knowledge of the nature of the proximate nitrogenous constitu- 

 ents present, the factor used in calculation may be changed, if such 

 change seems to be called for, while the original experimental work 

 still retains its value. 



In concluding this report the writer wishes to express the hope that 

 the method suggested, which seems to carry with it some improvement 

 upon present practice and in a fairly simple and easily applied form, 

 may be tried with yet other amids and proteids than those experi- 

 mented 011 by him, and that any special difficulties which may be en- 

 countered with particular articles of food may be investigated. Espe- 

 cially is it desirable that the variations be studied which may prove to 

 be necessary in dealing with vegetable instead of animal materials. 

 The latter have been chiefly kept in view, in accordance with the 

 instructions of the letter of authorization under which this investigation 

 has been conducted. 



