BIOLOGY OF BACTERIA. 55 



tinal walls to continue their existence and produce 

 greater damage than before. Some such theory may 

 explain the activity of such organisms as those of 

 typhoid and cholera, but it is not true that all bacteria 

 can be admitted into the intestinal structure in this way. 

 Before reaching the intestine the bacteria pass through 

 the stomach, and must resist the deleterious action of 

 the acid gastric juice, which few are able to do. Eichhorst 

 has reported an epidemic of typhoid fever that occurred 

 in a military barracks. In this epidemic the infection 

 seemed to take place through the rectum, and was traced 

 to the wearing of underclothing previously worn by 

 patients and improperly washed. 



(6) The Respiratory Tract. Notwithstanding the moist 

 interiors of the mouth and nose and the lashing cilia of 

 the pharyngeal and tracheal mucous membrane, large 

 numbers of bacteria enter the smaller bronchioles, and 

 sometimes penetrate as deeply as the air-cells. It is 

 unusual to find a section of healthy or diseased lung in 

 which no bacteria can be found. It seems to have been 

 proven by Buchner that micro-organismal infection may 

 take place through the lungs without definite breach of 

 continuity of the alveolar walls. He mixed anthrax 

 spores and lycopodium powder together, and caused 

 mice and guinea-pigs to inhale them. Out of the 66 

 animals used in his experiments, 50 died of anthrax 

 and 9 of pneumonia. Our knowledge of the disposition 

 of foreign particles in the lung probably explains such in- 

 fection by assuming that the presence of the lycopodium 

 attracted numerous leucocytes to the affected air-cells, 

 that these took up the powder, and with it the spores, 

 and that the leucocytes, being cells of very susceptible 

 animals, were unable to resist the growth into bacilli 

 of the spores which they had carried into the lymph- 

 channels. 



On the other hand, it has been shown that when 

 the entering spores are unaccompanied by a mechanical 

 irritant like the lycopodium powder, but are inspired 



