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598 



MARTIN — DISCUSSION ON CARCINOMA. 



are selected, in leprosy the large multinuclear leprosy cells, in tuber- 

 culosis the bacilli are nearly always found in giant cells, in the last 

 instances an active growth being apparent from the multiple nuclei. 

 It may, then, be asked with reason, if cancer be parasitic why the 

 epithelium calmot equally well be selected as a cellular habitat by 

 parasites just as the blood cells, etc., in other diseases. Advocates of 

 the parasitic theory of cancer find their organism constantly within 

 the epithelial cells and it is here that the proliferation occui's. 



Hitherto the instances given of hyperplasia have concerned cells 

 other than those of epithelial structure, but we do not by any means 

 lack an example where true epithelial overgrowths are induced by 

 parasitic invasions ; this is found in a disease of rabbits known as 

 coccidiosis. Since the researches of Malassez, Delepine and others it 

 has been recognized that certain parasites (whose form and general 

 character bear a striking resemblance to the supposed organism of 

 cancer) often infest the alimentary tract of ral)bits '\nd make their 

 way thence to the liver, where they invade the epithelial cells in the 

 bile ducts. As a direct result, an extensive proliferation of the epithe- 

 lial cells takes place and also of the tibrous stroma about them, so 

 much so that a luxuriant overgrowth occurs resembling very much a 

 malignant adenoma of the I'ectum. (v. fig. F and Nos. 1 to 7.) 



From what has been said, then, it seems clear that, firstly, parasites 

 are quite capable of producing cell proliferation independent of 

 inflammatory conditions, i. e., a proliferation analogous in general 

 features to cancer ; that, secondly, they produce metastases, as does 

 cancer ; that, in the third place, it is not uncommon to find parasites 

 selecting special cell structures for their habitat ; and that, finally, we 

 can find in the lower animals an epithelial overgrowth and the forma- 

 tion of a fibrous stroma, all being induced by the invasion of a 

 parasite. 



Before considering further the general reasons upon which the 

 parasitic theory of cancer may be based, I will briefly describe the 

 main characters of the organism supposed to be concerned in the 

 formation of cancer tumours, though the diagram kindly prepared by 

 Dr. Adami will perhaps better give an idea of their nature. In 

 attempting such a description one is beset with difficulties, owing to 

 the x'firious opinions among investigators as to what is and what is 

 not to be regarded as the true parasite. This confusion arises from 

 the supposed resemblance which certain other structures have to 

 these parasites ; among these may be mentioned forms of cell 

 degeneration, morbid karyokinesis of cancer cell nuclei, invaginated 

 cancer cells, enclosed leucocytes, and endogenous cell formations. 



