862 EXPEKIMENT STATION EECOKD. [Vol. 35 



six eggs could be eaten by dogs without the production of any of the symp- 

 toms resulting from the ingestion of the raw egg white. About 90 per cent 

 of the nitrogen in cooked eggs was utilized as compared with 50 to 70 per 

 cent in the case of the raw egg white. 



" The indigestibility of native egg white probably lies either in its anti- 

 tryptic content or in its chemical constitution. Its physical texture appears to 

 play a minor part in its behavior. 



" Of the individual proteins constituting egg white, the albumin fraction ap- 

 pears to be the indigestible component. 



" The whites of the hen's egg and duck's egg act alike in causing diarrhea 

 and in being poorly utilized. 



" Egg yolk either raw or cooked is excellently utilized. It sometimes causes 

 digestive disturbances in dogs, apparently because of its high fat content." 



The author states that the observations of earlier investigators, relied upon 

 by dietitians in supporting the use of raw eggs, have been misinterpreted and 

 that while raw whole eggs, raw egg white, and albumin water are excessively 

 l)rescribed in dieto-therapy there is little basis of fact for this practice, in view 

 of the data obtained in this investigation. 



An extended bibliography is appended. 



Feeding experiments on the substitution of protein by definite mixtures 

 of isolated amino acids, H. H. Mitchell {Jour. Biol. Chem., 26 (1916), No. 1, 

 pp. 231-261, figs. 5). — Experimental data obtained by other investigators on the 

 feeding of mixtures of amino acids to the exclusion of protein are re\'iewed at 

 length, and the author reports experiments undertaken for the purpose of 

 discovering some mixture of isolated amino acids which would be capable of 

 supporting life. Although the results of these experiments have not been 

 entirely successful, they have several points of interest. The results of the 

 investigation may be summarized as follows : 



Mice were kept alive for from 70 to 9S days by feeding alternately a ration 

 containing from 4 to 6 per cent of various mixtiires of isolated amino acids, 

 6 to 4 per cent sucrose, 34 per cent starch, 28 per cent protein-free milk, 10 

 per cent lard, and 18 per cent butter fat, and a ration containing 10 per cent 

 of sucrose with other constituents in the same proportion as the first. In 

 some of the experiments the mice practically maintained their weight for 

 periods of from 15 to 35 days. 



" The alternate feeding of an amino acid ration and a nonnitrogenous ration 

 (except for the nitrogen present in the protein-free milk) induced a better total 

 consumption of food than feeding with an amino acid ration alone, and in all 

 other respects led to more successful results. However, it is probable that in 

 no case was the amino acid intake sufficiently large to assure a fair test of its 

 adequacy. 



"Amino acid rations containing no added tyrosin, or no added tyrosin and 

 phenylalanin, did not give appreciably different results from rations contain- 

 ing these amino acids. However, if tryptophane was absent from an amino 

 acid ration the period of survival of mice fed this ration alternately with the 

 nonnitrogenous ration was noticealily shorter than the periods of survival of 

 mice kept on rations containing added trytophane. 



" Mice could be kept for much longer periods of time on rations containing 

 mixtures of amino acids, including trytophane and fed alternately with the non- 

 nitrogenous basal ration, than when fed the basal ration alone. Furthermore, 

 this difference in survival can not be accounted for by a difference in energy 

 intake. This fact has been interpreted as meaning that at least some of the 

 amino acids have specific functions in metabolism aside from that of serving 

 Bimply as material for the synthesis of body protein." 



