ALIMENTARY BACTERIA AND NUTRITION. 6 1 



are not ideal in composition. The inclusion of 20 to 45 per cent of 

 fat in the diet a condition necessitated by the requirements of the 

 experiments as outlined seems like an excessive amount; neverthe- 

 less the utilization appears to be satisfactory and attempts to devise 

 less objectionable modes of feeding have been unsuccessful in our 

 hands. 



ALIMENTARY BACTERIA AND NUTRITION. 



In the course of our later studies we have been forced to take 

 cognizance of the possible role of the bacterial flora of the alimentary 

 tract in relation to appropriate nutrition. The water-free, fat-rich 

 food characteristic of our experimental dietaries is not, broadly 

 speaking, a particularly favorable medium for the development of cer- 

 tain groups of bacteria. The food of our animals therefore probably 

 introduces into the digestive tube of the experimental animals bac- 

 terial invaders somewhat different from those which normally inhabit 

 the alimentary tract of rats living on a free mixed diet. It is quite 

 conceivable, therefore, that the bacterial conditions may be altered 

 markedly as a result of the restriction in the growth of certain groups 

 or the facilitation of the development of still others in the alimentary 

 tract under these changed and sustained conditions of altered diet.* 

 It is well known, for example, that in higher animals the preponder- 

 ance of acid-producing organisms to use a single illustration may 

 lead to an inhibition of the growth of the putrefactive group. 



Guided by such considerations and the observation that those 

 rats that have been maintained for long periods on diets with isolated 

 food-stuffs become koprophagists, we have initiated the plan of feed- 

 ing small quantities of the faeces of rats living on ordinary mixed food 

 to some of our experimental animals, particularly in cases where 

 symptoms of nutritive decline had become manifest. In nearly every 

 instance the occasional addition of a small amount of the faeces from a 

 normally fed rat at once stopped the decline in weight of the experi- 

 mental animals to which a single protein was being fed. The results 

 in almost all of these cases have been sufficiently striking to warrant 

 a further pursuit of this topic. In our experiments there appears to 

 be an unmistakable favorable influence induced by the occasional 

 addition to the dietary of normal faeces with their high bacterial 

 content. It must not be overlooked that other components besides 

 bacteria, notably inorganic salts and unknown compounds, are also 

 furnished by this means; but the quantities involved have always 

 been very small. Further investigation will be necessary and is 

 already projected. 



The procedure in the case of these faeces-feeding trials consisted 

 in introducing small amounts (about 0.5 gm.) of air-dry excrement 



*Cf. Herter and Kendall: Journal of Biological Chemistry, 1910, vn, p. 203; Kendall: 

 Journal of the American Medical Association, April 15, 191 1. 



