Abstract
In a prior paper 1 a method was described by which single phases of chemotherapeutic action could be studied separately∗. These phases are possibly due to interactions between (1) agent and parasite, (2) agent and host, and (3) host and parasite.
Working 1 with Bayer 205, weak solutions (0.5% and 0.05%) were allowed to act upon trypanosomes (Tr. equiperdum); then the parasites washed several times with a saline-broth mixture and rats infected with them. Control rats were infected with trypanosomes which had been treated similarly with saline-broth mixture only. If a small number of untreated trypanosomes were injected together with 10 times as many treated trypanosomes into one rat, and the small amount of untreated trypanosomes only into another, in all experiments both animals died at the same time and much earlier than rats which were infected with the large amount of treated trypanosomes only. This proved that Bayer 205, once bound, could not act upon other trypanosomes. Thus with Bayer 205, a direct action of the chemotherapeutic agent upon the parasites was demonstrated; only a decrease of virulence results. Similar experiments with arsenicals are described in the present paper.
It was to be expected that in this type of experiment, arsenicals would behave similarly to Bayer 205. Such was not the case. If an emulsion of trypanosomes was brought in contact with neo-arsphenamine dissolved in nutrient broth in a dilution of 1/5000, or with sodium atoxylate, and allowed to stand for 20 minutes, then centrifuged and washed, the trypanosomes remained almost as virulent as the controls. Time of action and dilution of the chemotherapeutic agent were chosen far below the limits which produce a damaging effect as shown by the change in motility.
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