76 HUMAN INTESTINAL PROTOZOA IN THE NEAR EAST 



not have divided. We have not obtained any evidence in support 

 of the view that the cysts are formed to enclose two conjugating 

 individuals. Whether such cysts occur or not is still undecided, 

 but it is perfectly clear that the majority of the cysts are formed 

 round single individuals. 



(11) Course of Lamblia Infections. 



It has already been shown that lamblia infections may persist 

 for several years, but during the course of such an infection the 

 flagellates or their cysts are not always to be found in the stools. 

 The cysts alone are usually found, and judging by these the infection 

 fluctuates, there being periods when the cysts are very numerous 

 and others when they are absent. We do not know whether this 

 absence of cysts from the stool means that the flagellates in the 

 small intestine are reduced in number, or whether there has been 

 a sudden cessation of cyst production. Nor do we know the cause 

 of this change. In watching the lamblia infections from day to 

 day a case, which has been passing a + + + infection of cysts 

 regularly for a fortnight or longer, will suddenly show a reduction 

 to + +, then to + , and then entire absence of cysts. Just as 

 suddenly after an interval of a week or more a few cysts will be 

 found and the infection will work up again to a large one. The 

 course of several lamblia infections is shown in the charts illus- 

 trating the cases of E. histolytica and flagellate infections accom- 

 panying this paper. 



Pathogenicity of Lamblia. Of all the flagellates of the human 

 intestine lamblia has the best claim to pathogenicity. This does 

 not mean that it always produces symptoms, nor that every one 

 with such an infection is to be isolated and treated as a dangerous 

 carrier. Such a course would be obviously absurd in time of war, 

 for there occur many healthy, able-bodied men who are carriers of 

 lamblia for every one who shows symptoms or is incapacitated in 

 any way by its presence. 



The reasons for regarding lamblia as pathogenic are not merely 

 the presence of the flagellates in diarrhoeic conditions, but the fact 

 that certain cases of lamblia infection have attacks of a character- 

 istic nature when they pass large quantities of yellowish mucus in 

 which occur unencysted lamblia in myriads. A small portion of 

 such mucus may show the flagellates lying over one another and 

 filling the entire microscopic field. Such attacks of diarrhoea with 

 mucus occur at intervals, and whenever the attack comes the same 

 mucus is passed with the same microscopical appearances. A case 



