AMEBIC DYSENTERY 135 



cent infection among returned American overseas troops in con- 

 trast to 3 per cent in home service troops. In India, on the other 

 hand, MacAdam estimates that one-third of the inmates of 

 hospital wards are infected with E. histolytica. 



Amebic Dysentery and Liver Abscesses. One of the most 

 serious menaces in the tropics is dysentery; people who have 

 always lived in temperate countries have no conception of the se- 

 verity of this ailment. In many tropical countries dysentery ranks 

 next only to malaria as a cause of death, and very often it finishes 

 the work of such diseases as malaria, kala azar and other fevers. 

 There are many different types of dysentery, especially in the 

 tropics, each showing somewhat different symptoms and having 

 to be treated in different ways. Some cases of dysentery are due 

 merely to improper diet, some to disturbances of the digestive 

 tract due to other diseases, and the majority to intestinal para- 

 sites of some kind, either bacteria, protozoans, or worms. In 

 a restricted sense " dysentery " is used for intestinal diseases 

 caused by bacteria or protozoans. The diseases caused by pro- 

 tozoans other than amebse are discussed in the chapter preceding 

 this. " Bacillary dysentery " is a bacterial disease and need not 

 be discussed here except in comparison with other types of dysen- 

 tery. It occurs in temperate as well as in tropical countries and 

 is very common in epidemic form in armies, prisons and asylums. 

 Amebic dysentery, on the other hand, is uncommon outside of 

 warm climates, but is of frequent occurrence in local areas in almost 

 all tropical and subtropical countries, where frequently a large 

 majority of dysentery cases are caused by amebae. The propor- 

 tion of cases of amebic dysentery to infections with the amebse 

 seems to be higher, and the disease more severe, in warm than in 

 temperate climates. Many of the cases of " trench diarrhea " 

 which occurred in France were a mild form of amebic dysentery. 



The role played by amebae in dysentery was in doubt for a 

 long time. The presence of amebae in perfectly healthy individ- 

 uals and the fact that amebse grown in artificial cultures would 

 never give rise to dysentery experimentally confused the problem. 

 There are several reasons for this confusion. In the first place 

 there are common species of intestinal amebae, especially Enda- 

 moeba coli and Endolimax nana which do not attack the tissues 

 or cause dysenteric symptoms, but which are easily confused 

 with E. histolytica. In the second place, non-parasitic amebae 



