Page:Popular Science Monthly Volume 79.djvu/439

Rh for his sustenance on his parents, brothers and sisters or remoter relations. At maturity, in addition to the possibility of becoming parasitic on his wife, he has a choice of many kinds of social parasitism. As a member of a trust, political party or legislative body, not to mention many other organizations and institutions, he may graft successfully on the community at large or on some particularly lucrative portion of it, and should he fail through these activities to store up a sufficient corpus adiposum in the form of a bank-account, he may parasitize, with advancing years and till the end of his days, on his own offspring.

But the roots of parasitism may be traced even deeper within the very fabric of the organism itself. The theories of Roux and Weismann have made us familiar with the struggle among the parts of the individual organisms, i. e., among its organs, tissues, cells and the components of its cells, a struggle in which these elements often grow and develop at the expense of other elements in a manner that can only be regarded as parasitic. The more modern theories of mutation and Mendelism, with their insistence on unit-characters and "factors," obviously admit of an interpretation in similar terms. We can even shift this interpretation to the psychic plane, where we find the fixed ideas, obsessions and monomanias behaving as so many processes which draw their sustenance from other psychic processes to such an extent that they may in the end not only dominate but destroy the whole personality.

Some of you will be shocked at this account of what we are in the habit of describing in very different language, for the same emotional reason that we all admire the tiger and the tiger-beetle and loathe the tape-worm and the louse, namely, because our instinctive horror of the parasites to which our species is so constantly exposed, prevents us even as twentieth-century zoologists from appreciating the extent to which all life, ourselves included, is saturated with parasitic proclivities. I fear, however, that this attempt to justify my shocking language will fail to convince some others among you, who will accuse me of being myself a host of one of the obsessions to which I have just alluded—of the parasitic obsession, namely, of the idea of parasitism. You will say that in thus subtilizing or volatilizing what has always seemed to be a concrete biological phenomenon, and in thus diffusing the concept