This conclusion is further supported by the disappointing result of the magnificent crusade of research for the discovery of the cancer "parasite," whether vegetable or animal, which has been pursued with a splendid enthusiasm, industry, and ability by the best blood and brains of the pathological world for twenty years past. I say disappointing, because a positive result--the discovery and identification of a parasite which causes cancer--would be one of the greatest boons that could be granted to humanity; not so much on account of the actual loss of life produced by the disease as for the agonies of apprehension engendered by the fact of the absolute remorselessness and blindness with which it may strike, and our comparative powerlessness to cure. So far the results have been distressingly uniform and hopelessly negative. Scores, yes, hundreds, of different organisms have been discovered in and about cancerous growths, and announced by the proud discoverer as the cause of cancer. Not one of these, however, has stood the test of being able to produce a similiar growth by inoculation into another body; and all which have been deemed worthy of a test-research by other investigators besides the paternal one have been found to be mere accidental contaminations, and present in a score of other diseases, or even in normal conditions. Many of them have been shown to be abnormal products of the cells of the body in the course of the cancer process, and some even such ludicrous misfits as impurities in the chemical reagents used, scrapings from the corks of bottles, dust from the air, or even air-bubbles. These "discoveries" have ranged the whole realm of unicellular life,--bacilli, bacteria, spirilla, yeasts, moulds, protozoa,--yet the overwhelming judgment of broad-minded and reputable experts the world over is the Scotch verdict of "not proven"; and we are more and more coming to turn our attention to the other aspect of the problem, the factors which cause or condition this isolation and assumption of autonomy on the part of the cells. This is not by any means to say that there is no causative organism, and that this will not some day be discovered. Human knowledge is a blind and short-sighted thing at best, and it may be that some invading cell, which, from its very similarity to the body-cells, has escaped our search, will one day be discovered. Nor will the investigators diminish one whit of their vigor and enthusiasm on account of their failure thus far.