Researches on the Intestinal Protozoa of Monkeys and Man

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Abstract
It will be convenient at this point, before proceeding to a more general discussion of the findings, to summarize all the experiments recorded in the eight preceding subsections. Briefly the results are as follows:(i) An attempt to infect a Macacus rhesus by feeding it with Trichomonas isolated from a monkey of the same species failed completely.(ii) Four similar attempts to infect a Macacus sinicus with the same Trichomonas (from M. rhesus) were equally unsuccessful.(iii) Two attempts to infect another M. sinicus by intra-intestinal inoculation with the same flagellate were likewise wholly negative.(iv) One attempt to infect a man per os with the same strain of Trichomonas (from M. rhesus) did not succeed.(v) A strain of Trichomonas from Man, when fed to a Macacus rhesus, produced no infection.(vi) The same strain (T. hominis) fed to a Macacus sinicus likewise failed to infect.(vii) A strain of Trichomonas from Macacus nemestrinus, however, when fed to M. rhesus, gave rise to a temporary infection lasting about a month.(viii) This Trichomonas (from M. nemestrinus, after passage through M. rhesus) produced, nevertheless, a permanent infection—lasting 4½ years to date—when fed to a man.(ix) The same strain of Trichomonas (from M. nemestrinus), after passage through M. rhesus and Man, when fed to a Macacus sinicus gave rise to an infection which endured for approximately 1½ months and then died out. But(x) The very same Trichomonas (which was derived from M. nemestrinus, and which produced a temporary intestinal infection in M. rhesus and M. sinicus, and a permanent intestinal infection in Man) when introduced into the vagina of M. sinicus established itself enduringly as a typical “T. vaginalis.” The infection has now persisted for ome 3⅓ years.(xi) The monkey (M. sinicus) in which a permanent vaginal infection with an intestinal Trichtomonas was established, has probably since reacquired no permanent intestinal infection—despite every natural opportunity for such reinfection.(xii) No macaque suffered any harm whatsoever as a result of inoculation with any strain of Trichomonas–whether successful or unsuccessful.(xiii) The one man successfully infected with Trichomonas (from M. nemestrinus) has likewise remained normal ever since.