DISCUSSION ON CARCINOMA. 



NOTES ON THE PARASITIC THEORY OF CANCER 



Bv C. F. Martin, B.A., M.D. 

 Demonstrator of Patholog> Gill University : Assistant Physician, Royal Victoria 



Hospital. 



So much has been written within recent years on the parasitic 

 nature of cancerous tumours, and the I'esults of investigations have in 

 some respects been so plausible that I thought I could best contribute 

 to the evening's discussion by briefly considering the possibilities of 

 this theory and observe on what grounds we may be induced to place 

 malignant tumours in the category of parasitic affections. While not 

 presuming to champion the advocates of this theory, inasmuch as my 

 experience is so limited, I will nevertheless endeavour to lay stress on 

 its most favourable features, many of which render the parasitic 

 nature of cancer something even more than a probability. We can- 

 not at all events repudiate the theory without a careful consideration, 

 for among its adherents are numbered two scientists whose names 

 stand foremost in bacteriology and pathology. Metchnikoff after ex- 

 amining the .specimens prepared by English and European investi- 

 gators emphatically pronounced in favour of the presence of parasites 

 in cancerous tumours, while Virchow is so strongly imbued with the 

 same idea that he is withholding his final volume on tumours, trusting 

 that the near future may bring increa'sed light on the etiology of 

 malignant growths. It must, however, be confessed that while per- 

 haps many observers are willing to acknowledge the presence of 

 parasites in cancer masses, they are less readily satisfied that their 

 presence is directly associated with the cause of the malady. 



Though it be true that the parasitic theory of cancer formations is 

 at present incapable of scientific proof, yet it should not be forgotten 

 that in many, indeed in the majority of our infectiour, diseases, we are 

 unable to carry out the postulates laid down by Koch to prove their 

 parasitic nature. The epidemic nature of some of course renders this 

 character probable, but in others even this feature is wanting. The 

 amoeba of dysentery is generally accepted as being the causative 

 factor of the tropical malady, yet the absolute proof is entirely want- 

 ing. Few scientists to-day will deny the relation between typhoid 

 fever and Eberth's bacillus, or of the plasmodium malariae to the 

 disease with which it is associated, yet in neither instance are we 

 positively enabled to fulfil the requirements necessary to establish 



