596 GASTRO-INTESTINAL BACTERIOLOGY 



are harmless to the host and more or less inimical to the bacteria it 

 is desirable to supplant, or by administering a diet which contains 

 appropriate nutritive substances in sufficient amounts to create con- 

 ditions favoring the development of normal intestinal bacteria whose 

 activities are in opposition to those it is desired to restrict or supplant. 



The effects of a monotonous diet maintained for considerable periods 

 of time upon the intestinal flora of a normal individual are clearly 

 shown in the normal nursling, where intestinal organisms are largely 

 carbohydrophilic and fermentative in character. Feeding experiments 

 in normal animals indicate that the development of a nursling intes- 

 tinal flora follows the prolonged administration of a nursling diet. 



If the intestinal flora to be modified does not contain sufficient 

 numbers of the desired types of bacteria, or if these latter organisms 

 are inactive, it may be important to reenforce the weakened or inactive 

 residual types with suitable cultures from without. Herter 1 was the 

 first to recognize the possibility of introducing desirable types of bac- 

 teria into the alimentary canal and Metchnikoff 2 has extended and 

 popularized this form of bacteriotherapy through his extensive studies 

 upon the effects of milk soured with the Bulgarian bacillus as a 

 therapeutic measure in excessive intestinal putrefaction. The Bul- 

 garian bacillus 3 is a large Gram-positive organism, which is non- 

 motile and forms neither spores nor capsules. It develops feebly in 

 ordinary media, but luxuriantly in milk, producing considerable 

 amounts of lactic and other acids, but no gas. It is a milk parasite, 

 having been perpetuated in this medium for many decades by the 

 Bulgarian peasants. 



The underlying principles of sour milk therapy as set forth by Metch- 

 nikoff are: a restriction of the protein in the diet, to reduce the 

 available putrescible material in the intestinal tract; and the adminis- 

 tration of liberal amounts of sour milk to flood the alimentary canal 

 with preformed lactic acid. It was originally believed that the Bul- 

 garian bacillus would become acclimatized in the intestinal tract and 

 continue to produce lactic acid from the ingested carbohydrate, thus 

 maintaining an acidity throughout the intestinal contents; this should 

 create conditions inimical to the development of putrefactive organ- 

 isms, which are said to be intolerant of acids. It is doubtful if the 

 Bulgarian bacillus does become acclimatized in the large intestines, 



1 British Med. Jour., 1897, ii, 1847. 



2 Prolongation of Life. 



3 See Rahe, Jour. Inf. Dis., 1914, xv, 141, for description and differentiation from 

 other aciduric bacteria. 



