132 THE PROTEIN ELEMENT IN NUTRITION 



of experiment by summing up the objections put forward to them, 

 and to any general adoption of dietaries containing the low level 

 of protein he advocates : 



1. The method of basing the protein requirements of the body 

 on the average amount of nitrogen eliminated in the urine gives 

 too low a result for the protein metabolism per kilo of body 

 weight. 



2. The very great variations recorded for the digestibility and 

 absorption of protein from identical diets for the individual 

 members of his second group men of the hospital corps can 

 either be explained on the basis of malnutrition of the intestinal 

 epithelium, the result of a diet poor in protein, or by failure of 

 the men to collect all the faeces passed each day, so that the 

 total amount included in the analyses was too low. For several 

 reasons we believe the latter to be the more likely explanation. 

 If this should be the explanation, it must throw a certain amount 

 of doubt on the collection of the daily urine for the five months 

 during which this experiment was carried out. Any loss of urine 

 would mean a seemingly lower level of nitrogenous metabolism 

 than was actually the case. It is well known how difficult it is 

 to save all the excretions, except where the most rigid precautions 

 are taken. In the work in India we found it absolutely necessary 

 to confine prisoners under observation to solitary cells, in order 

 to insure the complete collection of the urine and faeces. This 

 criticism would not apply to Chittenden's first and third groups 

 of subjects, who were educated men, and who would fully under- 

 stand the importance of saving the excreta in full. 



3. Whilst one feels bound to accept the figures stated for the 

 daily intake of nitrogen in the dietaries published throughout 

 Chittenden's book, at the same time one cannot help feeling that 

 they would have been much more satisfactory if the nitrogen of 

 those dietaries had been computed from analyses of the dry 

 food materials used, before being cooked, instead of being esti- 

 mated by means of factors for the percentage of nitrogen in 

 cooked food. The percentage of moisture in any cooked food 

 may vary very considerably from day to day ; this would be 

 specially marked with the more or less vegetarian types of diet 

 Chittenden was compelled to have recourse to in order to keep 

 down the protein content. 



Apart from these technical objections which could be easily 

 overcome, there has been considerable mass of criticism levelled 



