# Page:Popular Science Monthly Volume 83.djvu/419

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THE PROGRESS OF SCIENCE

larger, perhaps ethereal, existence and of the conditions regulating intercourse across the chasm. The speaker does not repeat the evidence on which he bases his faith, but it certainly has not produced similar conviction on others equally competent to judge.

CHEMIOTHERAPY AND DR. PAUL EHRLICH

In his address before the recent London International Medical Congress Dr. Paul Ehrlich, director of the Royal Institute for Experimental Therapy at Frankfort-on-Main, reviewed the problems of chemiotherapy. He said that the governing principle is that parasites are only killed by those materials to which they have a certain relationship, which substances are "parasitotropic." In the parasites and in the various organs of the body there are specific chemioreceptors which energetically attract certain fixation groups "somewhat as a magnet attracts iron." It depends on the relationship between the parasitotropism and the organotropism whether a certain disinfectant can be used as a remedy. The only substances that can be considered therapeutic agents are those of which a fraction of the tolerated dose is sufficient to bring about therapeutic effects.

This sounds rather obvious, and in fact Dr. Ehrlich, like Mr. Edison, appears to have accomplished his remarkable results by somewhat empirical methods. This procedure he defends in his address, saying at the outset that the important factors in experimental chemiotherapy are patience, skill, luck and money, and in conclusion: "Considering the enormous number of chemical combinations which must be taken into consideration in the struggle with disease, it will always be a caprice of chance or fortune or of intuition that decides which investigator gets into his hands the substances which turn out to be the best for fighting the disease."

Whether by chance or by intuition, by luck or by genius, Dr. Ehrlich, with the assistance of Dr. Hata and other fellow-workers in his Frankfort laboratory, in salvarsan, or "606," and neosalvarsan, or "914," has discovered drugs with remarkable therapeutic effects. Salvarsan is an arsenical compound with the formula ${\displaystyle {\ce {C12H12N2O2As2}}}$. Its effects on the spirochaetes of syphilis are well known, it having already been used in perhaps a million cases in all parts of the world. Cures are sometimes effected by a single injection in the first stages of the disease. It is not so well known that even more striking results have been attained with relapsing fever, the fever immediately subsiding after the injection of salvarsan, and the patients being cured by one injection. The very rare cases of recurrence are also readily curable. Dr. Ehrlich states that it is possible by one single injection of salvarsan to cure framboesia (yaws), which is caused by spirochaetes and is a scourge of the tropics, to cure it completely except in rare cases where unimportant relapses occur. Thus in Surinam a hospital in which over three hundred patients with framboesia were constantly under treatment was closed and turned to other uses after the introduction of the salvarsan treatment, as one single injection sufficed to cure the disease, and all the patients but two could be discharged.

In the concluding paragraph of his address Dr. Ehrlich said:

The efforts of chemiotherapentics must be directed as far as possible to fill up the gaps left in our defences, more especially to bring healing to diseases in which the natural powers of the organism are insufficient. And I believe that now definite and sure foundations have been laid for the scientific principles and the method of chemiotherapeutics, the way is visible before us—a way not always easy but yet practicable. In the diseases due to protozoa and spirilla extraordinarily favorable results have already been gained, as I have shown. There are many valuable indications that in a series of other diseases—small-pox, scarlatina, typhus exanthematicus, perhaps also yellow fever, and, above all,