BACTERIAL METABOLISM WITHIN THE BODY 693 



reduction the principal obstruction to the development of endogenous pro- 

 teolytic bacteria, as Bacillus proteus -and Bacillus mesentericus, is re- 

 moved, or at least greatly reduced. Also, the absence of lactose and other 

 utilizable carbohydrate at the level of the tract where Bacillus coli and 

 related forms are ino.it numerous forces these organisms to become pro- 

 teolytic in place of fermentative. The net result is an immediate increase 

 in proteolytic activity, and a decided extension of the proteolytic zone. 



Indol and other decomposition products resulting from the utilization 

 of protein for energy are formed in increasing amounts from the in- 

 testinal contents, and these may be absorbed from the tract and excreted 

 as aromatic sulphates or glycuronates into the urine. Peristalsis may 

 be, and frequently is, further reduced by this process, which tends to 

 become therefore of the magnitude of a vicious cycle. 



The biological basis for successful invasion of the intestinal tissues 

 by exogenous microbes is probably created or at least augmented hereby, 

 because available evidence indicates that intestinal invasion is more read- 

 ily accomplished when the proteolytic activities of bacteria exceed, or 

 replace, the normal fermentative processes. 19 



Bacteriologically considered, therefore, the normal nursling intestinal 

 flora reacts with breast milk in the alimentary canal in a manner analogous 

 to the natural souring of milk outside the body. Both are essentially 

 preservative processes. Milk soured by lactic acid bacilli does not readily 

 undergo putrefactive changes which render it unfit for human consump- 

 tion. Similarly* the normal intestinal contents of the normal nursling 

 do not appear to undergo putrefaction. 



The lactic acid, representing seme decomposition of lactose, has fuel 

 value for the body ; hence, it is not an entire loss in terms of the original 

 caloric value of the milk. In this respect, it is in sharp contrast with 

 the products arising from the degradation of proteins of milk by bac- 

 teria which do not ferment lactose. Such putrefactive products as are 

 known are either useless, or more or less harmful to the human body 

 when absorbed from the alimentary canal. 



It would appear therefore that a natural relationship exists between 

 the nature of the diet of the nursling and the character of the products 

 formed in the intestinal tract which are qualitatively those formed in the 

 natural or artificially induced souring of milk outside of the body. The 

 bacteria concerned are chemically, but not specifically, the same. Intes- 

 tinal conditions are unlike those outside of the body. This is true not 



the lactose, and to a much lesser degree from fats: for convenience, the lactic acid 

 will be mentioned as the principal product, and indicative of the entire group of 

 acidic compounds. 



18 The theoretical advantage of preparing patients for surgical operations, especially 

 those upon the large intestines, by the induction of a suitable fermentative flora in place 

 of a putrefactive flora is suggested. Of course this applies to operations which are 

 not omergency cases, since time is required to effect this change. 



