BACTERIAL METABOLISM WITHIN THE BODY 703 



their intestinal parasitism, quite as frequent passages of pneurnococci 

 through experimental animals are required to maintain their virulence. 



To summarize: there appears to be an abnormal state or condition, 

 more common in adults of middle age or older, in which available evidence 

 points to putrefactive products, the results of bacterial decomposition of 

 protein residues in the alimentary tract, as the underlying cause. This 

 state or condition is referred to by many as "auto-intoxication." 



If such be the case, the cure, or at least the arrest, of the morbid 

 process, naturally would be a restriction or prevention of the putrefactive 

 bacterial processes within the alimentary canal. The bacteria which are 

 known to produce indol, aromatic amins, and other similar putrefaction 

 products associated with the phenomena of auto-intoxication are for the 

 most part microbes of the colon-proteus-mesentericus groups. These bac- 

 teria produce the putrefaction products when they utilize protein or 

 protein derivatives for energy. When they utilize carbohydrate for 

 energy, these same bacteria produce lactic and other acids. If periods of 

 ebb and flow of carbohydrate occur in the alimentary canal, where these 

 organisms are abundant, there will be corresponding alternate periods of 

 putrefaction and fermentation. 



It follows that a continuous supply of the proper kind of carbohydrate 

 will result in a continuous production of lactic acid. Implantation with 

 normal intestinal lactic acid bacilli, as Bacillus acidophilus, with a con- 

 tinuous supply of carbohydrate, will tend theoretically at least to dimm- 

 ish the numbers of colon-proteus-mesentericus types, and restrict their 

 activities. Such a procedure probably will be found to be feasible in 

 a proportion of appropriate cases. 24 



Lactic acid or sour milk therapy has not yet reached its final develop- 

 ment. The brilliant conception of its possibilities as a contribution to 

 gastro-intestinal therapy is a monument to Metchnikoff's genius and con- 

 structive imagination. 



The discussion of intestinal bacteriology thus far has revealed two 

 distinct but related types of response to dietary alternations: First, a 

 change in the type of bacteria, as, for example, the dominance of Bacillus 

 bifidus in the normal breast-fed infant, and, secondly, the change in 

 metabolism as protein or carbohydrate is available for the energy require- 

 ments of the bacteria. The dominance of types is usually met with when 

 the diet is monotonous, and with a preponderance of one or another type 

 of energy-producing substance. In the case of milk in the normal nursling, 

 the seven per cent of lactose is the determining factor. On the other 

 hand, when the energy producing substance changes from time to time, 

 as for example in the lower levels of the small intestine of adults, where 

 periods of carbohydrate ebb and flow are superimposed upon a protein 



"Certain ill effects of unrestricted feeding of carbohydrate are discussed under 

 Endogenous Intestinal Infections, ride infra. 



