692 ARTHUR ISAAC KEXDALL 



trance through the mouth to the alimentary canal from various sources, 

 and their numbers up to the third day of life are determined chiefly 

 by their ability to grow in the fetal intestinal detritus, and the cholostrurn. 

 In temperate /.ones, the initial nucrobie growth is usually more luxuriant 

 in summer than in winter. 



On or about the third day after birth, the nature and appearance of 

 the alimentary niicrobic flora undergoes a clearly discernible change 

 (Tissier). The variety of forms arid dissimilarity of staining reactions 

 which characterize the postfetal flora give way to the dominance of a 

 rather long, slender bacillus with slightly tapered ends which rapidly 

 supplants the adventitious types. This is Bacillus bifidus (Tissier), a 

 lactic-acid-producing bacterium, characteristic of the intestinal and fecal 

 floras of a great majority of normal nurslings. It is worthy of comment 

 that Bacillus bifidus becomes prominent synchronously with the full flow 

 of the breast milk. Breast milk, it will be remembered, contains more 

 than six per cent of lactose, arid scarcely one and a half per cent of 

 protein. In addition to Bacillus bifidus, other bacteria in much smaller 

 numbers are found normally, Micrococcus ovalis, Bacillus acidophilus, 

 and even fewer members of the colon and lactis aerogenes groups [the 

 feces stained by Grain's at this time are strongly positive]. The author 

 has found that these organisms without exception can grow extremely 

 well in mediums rich in lactose, and they all produce considerable amounts 

 of lactic acid. The combined acidity arising from the utilization of 

 lactose for energy by these bacteria is the principal source of the acid 

 reaction characteristic of the normal intestinal contents and feces of the 

 nursling. Lactic acid, in the concentration normally present in the 

 intestinal tract, restrains the growth of endogenous proteolytic bacteria, 

 and it also restricts the development of exogenous, pathogenic microbes 

 which gain entrance to the tissues through the alimentary canal. 17 



When, for any cause, as for example decreased peristalsis, the lactose 

 is absorbed in the higher levels of the tract, a purely protein residuum 

 is left in the lower levels of the small intestine, and in the large intestine. 

 Under these conditions, the habitat of the obligate acidogenic bacteria 

 is restricted, and they are greatly reduced in number and in activity. 

 This follows through their inability to grow well in a residuum in which 

 protein derivatives are their only source of energy. 



The immediate effect is a greater or lesser reduction in the amount 

 of lactic acid 18 formed in the intestines, and in consequence of this 



"In this connection, the observations of the Medical Researck Committee that 

 dysentery bacilli may be isolated from dejections having a neutral or slightly alkaline 

 reaction, for days after they are excreted, are of interest. It was found that dysentery 

 bacilli could not be isolated from the same stools having an artificially induced acid 

 reaction (lactic acid) 5 approximately that of the normal nursling movement, even after 

 a few hours. 



"All the lactic acid bacilli appear to produce some acetic and formic acid together 

 with minute amounts of similar volatile decomposition products of the fermentation of 



