for the most part white blood cells, whose work it is to de- 

 fend the body from the attacks of disease-producing bacteria 

 and similar dangerous invaders. These cells have a chemi- 

 cal affinity for the bacteria and eat them up by merely flow- 

 ing around them and then digesting them. 



Frequently, however, the bacteria prove too much for the 

 phagocytes and are themselves the victors in the struggle. 

 In such cases there is serious congestion of the lymph 

 cavities and consequently nutrition is cut off from certain 

 portions of the intestinal wall. The cells of these portions, 

 therefore, die and are sloughed off, leaving ulcers or open 

 sores. From these ulcers bleeding occurs in proportion to 

 the size of the injured blood vessels which may lie in the 

 affected region and these hemorrhages constitute a serious 

 feature of the disease. 



The ulcers vary in depth, some being very shallow and of 

 little importance, while others may extend through the 

 whole muscular coat of the intestine and be separated from 

 the body cavity only by the thin peritoneal membrane. 

 These deep ulcers are the cause of a large proportion of the 

 fatalities resulting from the disease, for perforation of the 

 peritoneal membrane means a general infection of the body 

 cavity from the contents of the intestine and an immediate 

 and very serious surgical operation is then the only recourse. 

 Until these ulcers are thoroughly healed solid food or muscu- 

 lar exertion of the slightest nature is likely to cause perfora- 

 tion. 



The intestinal ulcers and the resulting hemorrhages, how- 

 ever, do not constitute the only serious feature of the dis- 

 ease, for the bacilli are carried by the blood and lymph to 

 all parts of the body, resulting in a general systemic infec- 

 tion. The bacilli themselves do no direct injury to the body 

 but, being living organisms, they produce waste products, 

 and these are decidedly poisonous to the body tissues 

 and are known as "toxins." The toxins are formed in large 



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