PART II. CHARACTERS AND DIAGNOSIS 55 



not, it shows that an infection may disappear for a considerable 

 period. In none of these cases was the infection a large one. On 

 the other hand, in the great majority of our cases which were 

 controlled for a week or ten days before treatment was commenced 

 there was no tendency for the infection to disappear as in such 

 cases as that of Healy who was controlled for nearly three months 

 and was rarely free from cysts of E. histolytica. 



(b) What Percentage of Carriers pass on to an Acute Dysenteric 

 Condition .' This question is even more difficult than the preceding 

 one, for an answer can only be obtained by controlling cases for 

 long periods and this has not yet been done to any extent. It is 

 clear that many cases can carry their infections for, at any rate, many 

 months without symptoms and it is equally clear that others may 

 have repeated attacks of dysentery in a similar period. Between 

 these two extremes there are many intermediate types where 

 infected individuals have mild attacks of diarrhoea with or without 

 mucus in the stool, which may or may not be the result of the 

 E. histolytica infection. A certain number of carriers complain of 

 pain over the large intestine or of other symptoms which are 

 difficult to explain except on the assumption that some intestinal 

 ulcers exist. Others say that they never pass a really formed stool. 

 It is perfectly clear, however, that a large percentage of men who 

 are stationed even for a short time in Egypt become infected with 

 E. histolytica. A certain though yet unknown, but by no means 

 negligible, percentage of these pass on to a condition of amoebic 

 dysentery and have to be invalided from the Service. It is evident, 

 therefore, that in the transference of new troops from England to 

 non-infected centres, it is inadvisable to station them in the first 

 place in endemic centres of amoebic dysentery like Egypt unless 

 important military requirements leave no other alternative. 



(c) What is the Condition of the Large Intestine in the 

 Carrier / It has been suggested that E. histolytica can live in the 

 large intestine as E. coli does without producing any lesion of the 

 gut, and that this is the condition of affairs in the carrier cases as 

 distinguished from the amoebic dysenteries who have definite 

 ulcerations. It seems, however, very doubtful if this is actually 

 the case, for many facts seem to indicate that some ulceration of 

 the intestine exists in these cases, though it produces no symptoms. 



It is a well-known fact that at post-mortem examinations in 

 countries where amoebic dysentery is endemic, amoebic ulceration 

 of the large intestine is often encountered in cases in which 

 there is absolutely no history of previous dysentery. In 1910 



