Fig. 3. Papillary Adenocarcinoma of Ovary, showing Intracellular Ameboid Forms of Parasites. (From N. Y. State Path. Lab. Rep.)
2. The Analogy Afforded by the Infectious Granulomas.
—These are universally conceded to be of parasitic origin, while their clinical course and behavior in every respect make many of them almost as malignant as the true cancers become.
3. Metastasis.
—This is in every other disease considered to be one of the most significant expressions of infection, yet until recently few of those who have willingly accorded to metastasis its now common interpretation in tuberculosis have been willing to give it the same dignity as a factor in the spread of cancer and an important explanation of its nature. Why should every other disease characterized by metastasis be everywhere viewed as parasitic, and cancer, in which occur some of its most positive expressions, be denied? Metastasis has the force and significance of an inoculation experiment performed under favorable circumstances.
4. Evidence of Local Infectivity.
—The involvement of a part which has lain in contact with a cancerous lesion, as about the mouth or the vulva, and in many other ways and places of which medical literature is now full, and the instances of cancer following the knife wound, especially following the track of the trocar used for tapping a case of cancerous ascites, stamp the disease as having an infectivity which cannot be explained on any inherent property of its own.
5. Microscopic Appearances.
—While it is true that but few observers have been able to agree upon a definite cancer parasite, it is also true that many of the best observers have seen, described, and figured bodies that do not belong in the cells of a cancerous growth except they are there in the roll of active agents, and the appearances which have been described by Pfeiffer, Plimmer, Gaylord, Calkins, and others are not to be explained away as mere artefacts, but must be given a place in our estimation which they would attain of themselves, as exciting suspicion, were there no other facts corroborating the views that they are in some way actively connected with the production of the disease. (See [Plates XIV], [XV], [XVI].)