110 THE ACUTE SELF-LIMITED INFECTIONS 



finally softens from the effect of the bacilli. When 

 the softened part separates and is removed, a ragged, 

 punched-out ulceration remains. This ulceration may 

 be progressive and eat into bloodvessels, causing 

 intestinal hemorrhage so common in this disease. If 

 the ulceration be directed out toward the peritoneal 

 surface of the intestine, perforation and peritonitis 

 may ensue. The presence of the typhoid bacilli and 

 their toxins in the organs, notably the spleen, causes 

 characteristic changes which need not be dwelt upon 

 here. 



Typhoid fever is more common in men between the 

 ages of twenty and thirty-five years. Spring and 

 autumn are the seasons of greatest prevalence. It 

 spreads from patient to patient usually through the 

 intervention of food and drink. Polluted water and food 

 infected by flies that have soiled their bodies upon ex- 

 creta, form the greatest sources of indirect propagation. 

 Water is polluted by the dumping of sewage containing 

 typhoid germs into a water course used as a drinking 

 supply. Typhoid bacilli can live within a particle of 

 feces over the winter, so that the infection of a water 

 course in the spring is not to be wondered at. When 

 winter breaks up the spring rains wash down the hill- 

 sides, sweeping before them surface collections into 

 streams. The greatest danger, however, exists when 

 towns empty their sewerage systems into a stream 

 from which other communities lower down take their 

 domestic supply. This means of spread is proven by 

 the fact that when known infected sewage is no longer 

 dumped into a water supply typhoid fever ceases 

 to be prevalent among the users of the water. Ice is 



