180 PATHOGENIC BACTERIA 



in food through the hydrochloric acid of the stomach. 

 This is also true of the typhoid bacillus. It will 

 multiply in feebly acid or alkaline solutions. Direct 

 sunlight kills almost at once, while diffuse light is 

 withstood for a long time. 



The colon bacillus is found in the intestines of 

 man and animals in health or disease. It is expelled 

 with the feces and therefore gets into water-courses. 

 The bacilli may be found in the superficial layers of 

 the earth. Examination of water for public health 

 purposes aims at its discovery as an indication of 

 sewage pollution. Its presence in milk may be ac- 

 counted for by contamination of milk in cans washed 

 with polluted water. It should not be forgotten that 

 despite the greatest personal care, colon bacilli are 

 widely distributed on everything that comes in contact 

 with man and animals. The newborn baby's intestine 

 is free of them, but does not long remain so, as the 

 organisms find their way in with food, from the hands 

 of attendants, or possibly through the anus and up the 

 rectum. The colon contains most of the bacilli and 

 the number decreases upward in the small intestine 

 until in the stomach they are rarely found. They may, 

 however, at times enter the liver by means of the 

 bile passages or portal vein system. 



The constancy with which the colon bacilli are 

 present in the intestine raises the question as to their 

 function or value there. This is probably best answered 

 today by saying that they assist in controlling the 

 growth of certain putrefactive bacteria, and that they 

 may assist somewhat in breaking up simple substances 

 so that these mav be more easilv absorbed. 



