TRICHOMONAS HOMINIS 653 



Infection of Animals. — Several observers claim to have infected animals 

 with T. hominis. Thus, Escomel (1913) stated that he had succeeded in 

 infecting the rabbit, guinea-pig, dog, and cat. Lynch (1915a) thought 

 he had infected rabbits by injecting them per rectum with cultures, but 

 in a later paper (1922) he doubts his original claim, owing to the difficulty 

 he has had in positively excluding a previous infection in animals. Boyd 

 (1919) stated that he had infected a rat by feeding it with cultures of 

 Trichomonas. Owing to the doubt which attaches to these experiments, 

 Hogue (1922) attempted to infect cats, kittens, and rabbits which had, 

 by repeated examinations, been proved to be free from Trichomonas 

 infections. The animals were fed and injected per rectum with cultures of 

 the flagellates, but in no case did an infection result. Kessel (1924a) 

 states that he has infected monkeys. 



Pathogenicity. — The fact that T. hominis occurs most commonly in 

 diarrhoeic stools has led observers to regard it as a pathogenic organism. 

 When there is no diarrhoea, the flagellate is still present, though it is only 

 rarely found in formed stools. As the cysts are not known, its presence 

 can be recognized only when diarrhoea occurs or after the administration 

 of a purge. It frequently happens that individuals suffer from a chronic 

 looseness of the bowel, and that no explanation of this condition can be 

 discovered. In a certain number of such cases T. hominis is present in 

 the stools, and many clinicians assume that they are the exciting cause 

 of the disorder. As there are many cases of this type in which flagel- 

 lates cannot be discovered, it is quite illogical to assume that the few in 

 which they are present owe their condition to these organisms. 



The writer (1920) examined by section post-mortem material from 

 five cases of T. hominis infection. In one of these the large intestine 

 showed the flagellates in the lumen of the glands, actually breaking through 

 the glandular cells, and distributed in the interglandular connective tissue 

 (Fig. 267). Whether this invasion of the tissues of the intestinal wall is an 

 indication of pathogenicity or not cannot be stated. It is possible that 

 the Trichomonas invaded the tissues shortly before or even after death. 

 It may be mentioned, however, that guinea-pigs, which are commonly 

 infected with T. cavice, often show ulceration of the large intestine and 

 csecum, with definite invasion of the tissues by the flagellate in perfectly 

 fresh material which has been taken from animals which have been killed. 



That invasion can occur at other times is borne out by an observation 

 made by Pentimalli (1923). Examining fllms made from blood taken from 

 a patient's vein under aseptic conditions, he found Trichomonas present. 

 A further examination made ten hours later showed the same organism in 

 smaller numbers. Further examinations were negative. No information 

 as to the presence or absence of an intestinal infection was obtained. 



