PART II. CHARACTERS AND DIAGNOSIS 81 



The difficulty of controlling such an infection is all the greater as 

 encysted forms are not known. With lamblia and tetramitus for 

 instance, infection can be recognized by identifying the encysted 

 forms when the free forms are absent in the constipated or formed 

 stools. With trichomonas, on the other hand, one very rarely finds 

 evidence of infection other than in the soft unformed or liquid stools. 

 Apart from the intermittency of the infection dependent on the 

 character of the stool, there seems to be a real one when flagellates 

 may be absent for days together even when the stools are quite soft 

 or liquid. In one case (Howard) trichomonas was present prac- 

 tically continuously for over three weeks, when it vanished not to 

 reappear during the following three weeks. This was the longest 

 period we have observed of the continued presence of trichomonas 

 in the stool. In another case (Pointer) trichomonas was only absent 

 for a few days at a time during an observation of sixty-two days. 



(16) Pathogenicity of Trichomonas. 



As already explained, this flagellate is hardly ever found in any 

 but softer liquid stools, and it is this reason which has led observers 

 to regard it as pathogenic" It is quite possible that sometimes 

 a flagellate produces symptoms of diarrhoea resulting from an 

 irritation produced by large numbers of organisms, but we are con- 

 vinced that in the majority of cases of diarrhoea its presence is only 

 accidental, and that it is fixed upon as the cause of trouble because 

 id happens to be the most conspicuous organism in the stool. In 

 an examination of 263 hospital cases where the stool was liquid 

 trichomonas was only found in eight, while of 393 with soft 

 unformed stools it was found in fourteen, and in 165 stools con- 

 sisting of blood and mucus it was found in three. There is very 

 little difference in any of these figures, though they are distinctly 

 higher than the findings in healthy men given in an earlier part of 

 this paper. This is only to be expected when one remembers 

 that the percentage of liquid and soft stools among the healthy 

 men is much lower than amongst the hospital cases. In the cases- 

 which had blood and mucus in the stool the trichomonas was 

 certainly not the cause of the dysenteric symptoms, yet the liquid 

 and soft stools did not show a definitely higher proportion of tricho- 

 monas cases. From these figures there is to be gathered nothing 

 which will support the pathogenicity of trichomonas. In warm 

 countries where practically every incoming white man suffers from 

 periodic attacks of diarrhoea, either from indiscretions of diet, 

 exposure, or other causes, it is not surprising that trichomonas 

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