TRICHOMONADS: HOST-PARASITE SPECIFICITY 



caecal contents, and this leucocytosis suggests patholog- 

 ical conditions which may be caused by this flagellate." 



There has been considerable discussion regarding the 

 tissue-invading powers of trichomonads (Haughwout, 

 191 8; Hadley, 191 7), but very little actual data are avail- 

 able. Wenyon (1920) made a histological study of the 

 intestinal wall of 5 patients who had died of pneumonia 

 and were infected with trichomonas. 'There were no 

 noticeable lesions of the intestine which one could attrib- 

 ute to the flagellates." Not only were the flagellates dis- 

 tributed over the surface of the mucosa but were also 

 found in the lumen of the glands of Lieberkiihn, in some 

 cases in large numbers. Definite ruptures of the glandu- 

 lar epithelium were noted in one case and the tricho- 

 monads "were evidently passing through these." "The 

 flagellates were scattered about in the interglandular 

 loose connective tissue, so that there was a definite inva- 

 sion of the tissues of the gut." "There never appeared 

 to be an extension of the invasion beyond the mucous 

 layer. Furthermore, there did not seem to be any reaction 

 on the part of the tissue as regards cell proliferation 

 or invasion." If we consider an organism pathogenic 

 that injures the tissues of its host, then Trichomonas 

 hominis may in certain cases be pathogenic; but we do 

 not know how often it invades the tissues nor whether 

 this invasion is sufficient to bring about the condition 

 known as flagellate diarrhea. 



(4) HosT-PARASiTE SPECIFICITY. Many of the lower 

 animals, such as rats, mice, dogs, cats, and guinea-pigs, 

 are infected with trichomonads apparently belonging to 

 species that differ from those in man. Thus far attempts 



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