INFECTION AND INTOXICATION. 77 



adjunct in the diagnosis of gastric carcinoma. Its oc- 

 currence does not depend upon the carcinoma, but upon 

 conditions more common in carcinoma than in other 

 gastric diseases. The loss of natural acidity favors the 

 growth of the bacillus, which in its turn evolves lactic 

 acid. 



The intestine is the normal habitat of a number of 

 species of bacteria, some of which are temporary, some 

 permanent. The former are, for the most part, bacteria 

 that have entered with the food and drink, escaped' de- 

 struction in the stomach, and multiplied on their way 

 down the intestine. The permanent residents enter 

 shortly after birth, and, being particularly well adapted 

 by nature for intestinal parasitism, establish them- 

 selves permanently. The most common of the per- 

 manent residents are the Bacillus coli communis, Ba- 

 cillus lactis aerogenes (especially in milk-fed babies), 

 and the Streptococcus coli gracilis (especially in meat- 

 eaters). It seems to be true that carnivorous animals are 

 inhabited by a greater number of intestinal parasitic bac- 

 teria than herbivorous animals ; also that the colon is the 

 home of a greater number than are found in any other 

 part of the intestine. 



It has often been suggested that the bacteria of the di- 

 gestive tract are essential to life in that they assist the 

 function of converting proteid substances to peptone. 



To determine the truth of this, Nuttall and Thier- 

 felder 1 performed an interesting experiment. A preg- 

 nant guinea-pig was delivered of its young by Cesarean 

 section, and one of the offspring immediately transferred 

 with sterile instruments to a sterile chamber, where it 

 was kept and fed upon sterile milk. After a number of 

 days, during which it lived comfortably, it was killed and 

 its organs subjected to careful examination. The intes- 

 tinal tract was found to be entirely free from bacteria. 

 From this the experimenters conclude that bacteria are 

 not essential to intestinal digestion. 



1 Zeitschrift fur physiol. Chemie, 1896, Bd. xxii., Hefte 2 und 3. 



