SOURCES OF INFECTION 39 



This is particularly the case during the last stages of diseases, not 

 necessarily infectious, such as chronic heart disease, kidney 

 disease, or diabetes. Vital resistance is much lowered, and intes- 

 tinal bacteria, invading the tissues in enormous numbers, set up 

 what is known as terminal infection, which is often the immediate 

 cause of death. 



The stomach with its gastric juice, containing during digestion 

 .2 percent to .3 percent of hydrochloric acid, guards the lower ali- 

 mentary tract against infection. A great many bacteria are in- 

 gested with foods, particularly with milk, cheese, and overripe 

 fruit. These in the most part are quickly destroyed by the hy- 

 drochloric acid. When the stomach is diseased and the contents 

 become stagnant, as in stenosis of the pylorus, and in carcinoma, 

 when HC1 is diminished, or absent, fermentative bacteria give rise 

 to great amount of gas, and lactic acid, to the great discomfort of 

 the patient. The normal acidity of the stomach is a great 

 safeguard against infection with cholera. If tubercle bacilli are 

 swallowed, and if infection occurs, the lesion is not always localized 

 to the alimentary tract. Lesions of the lymph glands, peritoneum, 

 bones, and nervous tissues often follow the ingestion of these or- 

 ganisms. Dogs fed on soup containing great numbers of tubercle 

 bacilli, and then killed three hours after, were found to have bacilli 

 in the thoracic duct. Chyle from the duct, injected into guinea 

 pigs, caused tuberculosis in them (Nicolas and Descos). 



The interior of the uterus, the bladder, urine, deep urethra, and 

 lungs are generally sterile in health. With the exceptions noted 

 where germs are not usually found, all tissues, especially the inlets 

 and outlets of the body, may be said to have a normal bacterial 

 flora. Bile has a distinct antibacterial power, which indeed is one 

 of its functions in the intestines. 



The placenta is an avenue of infection in several diseases: not- 

 ably small-pox, anthrax, glanders, typhoid fever, and sometimes 

 tuberculosis pass through the placenta from mother to foetus. 

 Streptococci may pass through the placenta of a woman with 



