GASTRO-IXTESTINAL FLORA OF NORMAL INFANTS 677 
forms neither spores nor caj)siiles. It develops feebly hi ordinary 
media, but luxuriantly in milk, producing consideral)le 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 administration 
of liberal amounts of sour milk to flood the alimentary canal \\ith 
preformed lactic acid. It was originally believed that the Bulg rian 
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 C(mtents; this should create con- 
ditions inimical to the de^■elopment of putrefactive organisms, which 
are said to be intolerant of acids. It is doubtful if the Bulgarian 
bacillus does become acclimatized in the large intestines, where putre- 
factive action is maximal.' The theoretical and practical difficulties 
of acclimatizing a milk parasite in the intestinal tract would suggest 
that a normal intestinal organism of the lactic acid type, as B. acido- 
philus'- (whose habitat is the large intestine), would be theoretically 
more efficient in those cases where Bacteriotherapy is indicated. It 
is very essential that the culture of B. acidophilus used for intestinal 
implantation shall be of recent isolation from the intestinal tract. Old, 
stock cultures grown upon laboratory media for long periods of time 
lose their ability to grow in the intestinal environment.'^ 
Bromatherapy.'*— The very direct and striking relation between 
the nature of the food of bacteria and the character of their products 
of metabolism has an important theoretical and practical application 
in relation to intestinal bacteriology in health and disease. It has 
been stated in another section that products of bacterial metabolism 
harmful to the host may be classified as nitrogenous compounds or resi- 
dues derived from proteins and protein derivatives, and non-nitrogen- 
ous compounds derived from carbohydrates and fats. The former are 
produced by bacteria acting upon proteins and their derivatives in 
the absence of utilizable carbohydrates; the latter are formed by 
bacteria which are utilizing carbohydrates or fats. Thus, the diph- 
theria bacillus forms a powerful toxin in protein media, but does not 
form toxin when available carbohydrate is added to the medium; 
B. coli forms indol in protein media, but does not form indol when 
available carbohydrate is added to the medium. If these bacteria were 
developing in the intestinal tract at levels where a continuous supply 
of carbohydrate could reach them it would be theoretically possible to 
1 Herter and Kendall: Jour. Biol. Chem., 1908, 5, 29;i. Raho: Jour. Inf. Di.s., 1915, 
16, 210. 
2 Rotch and Kendall: Am. Jour. Dis. Child., 1911, 2, .30. 
3 Kendall and Haner: Jour. Infee. Dis., 1924, 35, 89. 
* Kendall: Dietotherapy, Chap. VII. 
