32 THE POPULAR SCIENCE MONTHLY 



to be decisive would have to be conducted not merely on people in 

 good health, but also on a suitable variety of digestive and nutritional 

 disorders in which the bacterial conditions in the intestine, the state 

 of metabolism and the general conditions of life are taken into account 

 with the greatest care and judgment. Although I have for many 

 years been interested in watching the influence of fermented milk on 

 the human organism in various states of digestive derangement, and 

 have accumulated many observations bearing on the question, my 

 experience falls far short of what is necessaiy to establish final con- 

 clusions. In this communication, therefore, I do not ofPer any solu- 

 tion of the therapeutic problems pertaining to the use of fermented 

 milks, but seek only to discuss critically, in the light of such informa- 

 tion as now exists, some of the claims that have been made for the 

 employment of these kinds of milk. I do this with the thought tliat 

 a discussion of the various elements which should enter into the forma- 

 tion of a Judgment regarding the therapeutic value of milk subjected 

 to lactic acid fermentation may prove helpful to those who have not 

 given the subject much personal study and are therefore unable to 

 analyze the problem in a way that is likely to serve as a practical guide. 



There are five important kinds of effects referable to the action of 

 fermented milks which must be considered in any judgment of the 

 therapeutic effects of a milk which has undergone lactic acid fermenta- 

 tion. These are, first, the effects on the absorption of fats and pro- 

 teins; secondly, the effects due to reduction of carbohydrates; thirdly, 

 effects due to the presence of lactic acid; fourth, effects due to the 

 bacteria used in lactic fermentation; fifth, effects due to a lowering of 

 putrefactive decomposition. These latter effects, which are of the first 

 importance in connection with any study of the action of fermented 

 milk, are of course not entirely distinct from the others just men- 

 tioned, but stand related to each of these other factors. Owing to their 

 prominence, however, it is desirable that they should be separately 

 considered. 



At present the influence of lactic acid fermentation upon absorp- 

 tion of the milk constituents is but little understood. The question 

 relates especially to the absorption of fats and of proteins, for the 

 carbohydrates of the milk are in large degree removed by the fermen- 

 tative process, lactic acid, carbon dioxide and alcohol being the chief 

 constituents resulting from the breakdown of the milk sugar. It is 

 important that we should obtain exact data with regard to the absorp- 

 tion both of the fats and of the proteins, but, so far as I am aware, 

 these do not at present exist. If it could be shown that the absorption 

 of milk fat and of milk proteins is increased in health through the 

 influence of lactic acid fermentation of any kind, this would be a dis- 

 tinct argument in favor of the use of such milk as an article of diet. 



