THERAPEUTIC ACTION OF FERMENTED MILK 35 



acid it is reasonable to suppose that the use of lactic acid in weak 

 concentration exerts some anti-fermentative action, especially against 

 such microorganisms as do not readily grow in acid medium. But 

 there are many kinds of microorganisms in the digestive tract «which 

 are resistant to the action of lactic acid in the low concentration which 

 can be tolerated by a somewhat irritable mucous membrane. Most 

 yeasts and some important intestinal bacteria, such as B. lactis cerogenes, 

 B. hifidus, B. infantilis and various organisms classed at acidophiles, 

 have this property. It is a fact little known that some of the coccal 

 organisms of the intestine resist the action of acid in a remarkable 

 measure. It is therefore quite clear that anything approaching a 

 significant modification of the activities of organisms of the types just 

 mentioned is not to be looked for through the use of lactic acid. More- 

 over, I have shown that a considerable grade of acidity in the intestinal 

 tract is consistent with very active fermentative growth of B. cerogenes 

 capsulatus. This organism forms butyric acid during the fermentation 

 of carbohydrates, together with only small quantities of lactic acid, and 

 there is no reason to suppose that its development in the intestine is 

 materially inhibited by any concentration of lactic acid which is likely 

 to be obtainable in the lower part of the small intestine or in the colon, 

 either as the result of administering lactic acid or in consequence of 

 the use of soured milk. 



That a considerable or high degree of putrefactive decomposition in 

 the intestine is not controllable in man by the administration of 

 moderate doses of lactic acid has become plain to me as the result of 

 clinical observation. And that even very large doses of lactic acid are 

 unable to restrict intestinal putrefaction is rendered highly probable 

 from experiments made in my laboratory by Dr. Helen Baldwin. In 

 dogs taking a meat diet and excreting urine characterized by abundant 

 indican and high ethereal sulphates there was no falling off in putre- 

 faction as a result of administering doses of lactic acid as large as 

 five grams daily. It seems to me doubtful if under these circum- 

 stances enough lactic acid could reach the large intestine to exert even 

 a moderate anti-putrefactive action. The experiments just mentioned 

 represent an extreme case, since they were made on animals living ex- 

 clusively on meat. The results obtained can not, therefore, be regarded 

 as strictly applicable to man. Nevertheless these experiments are in- 

 structive as indicating the inefficacy of large doses of lactic acid in 

 controlling intestinal putrefaction where the conditions for such putre- 

 faction are favorable and where the acid is given under conditions 

 rendering likely its absorption in the upper part of the digestive tract. 



That the presence of lactic acid in soured milk does not necessarily 

 exert a significant anti-putrefactive action in the large intestines is 

 clearly shown by the observation which I have several times made that 



