To summarize the results obtained from these experiments, one may say that N-phenylglycineamide-p-arsonic acid is capable of exercising a very definite effect upon the course of infections produced by spirochetes of the recurrens group and by Treponema pallidum. It is more difficult to say, however, just how these effects should be interpreted. In the case of the blood spirochetes, the infection is ameliorated, and even though the spirochetes are not immediately destroyed, the infection is frequently brought to a termination which leaves the animal in a condition not unlike that produced by more powerful spirocheticidal agents. That is, the infecting organisms are either affected in such a way that they eventually die off or are destroyed by the host in such a way that no lasting immunity is developed in consequence of their destruction.
Apparently much the same type of reaction occurs in the treatment of rabbits infected with Treponema pallidum. It is possible that when very large doses of the drug are used, these organisms may be completely destroyed, but it is certain that in other cases, where complete healing of the lesions is accomplished as a result of treatment, the organisms are not destroyed. Moreover, it appears that such a result can be accomplished in the presence of numerous actively motile spirochetes, and once the effect of the drug has reached this point, either the capacity of the spirochetes for stimulating reaction on the part of the tissues is lowered or else the reactivity of the tissues is reduced. At any rate., living spirochetes may remain in the tissues for considerable periods of time without giving rise to the usual tissue reaction which characterizes these infections.
With either group of organisms, therefore, N-phenylglycineamide-p-arsonic acid appears to act in a manner somewhat different from that of the usual spirocheticidal agents. While it does possess a considerable degree of spirocheticidal action, its chief effect is seen in the peculiar manner in which it modifies or controls the course of these infections.
Further than this, we shall not attempt to go at present. As set forth in the literature, the facts and principles upon which such experiments depend are so few as to offer almost no basis for an interpretation of these experiments. When we have had an opportunity of reporting our own experience in dealing with these infections, we may return to a consideration of the facts here reported.