SHORT PAPERS 385 



Hum; it is impossible that a parasitism can exist here in the same way as in the 

 well-known parasitic diseases, such as the pyemic diseases or the infectious 

 granulomata. Pus is a local formation, whether in a primary or a metastatic 

 abscess, tubercles, gummata, nodules of leprosy, and actinomycosis, etc., are 

 purely local formations wherever they grow, whether they are primary or sec- 

 ondary. No cellular connection exists between primary and secondary abscesses, 

 between primary and metastatic tuberculous masses. 



That pus, tubercles, etc., may arise, it is sufficient that pus cocci, tubercle 

 bacilli, etc., arrive at a certain place. For the formation of secondary cancer it is 

 absolutely necessary that cancer cells from the primary tumor, or from a second- 

 ary tumor originating in the same way, arrive at the spot, and continue their 

 growth. In secondary cancers there is an effectual transplantation of cancer cells, 

 in suppuration, tuberculosis, etc., a transplantation of parasitic organisms, which 

 do not themselves constitute the new lesion but cause definite phenomena in 

 the local tissue without any cooperation of tissue from the primary lesion. Thus, 

 there exists between these two groups of processes an essential difference, and we 

 cannot conclude that because parasites play a role in abscesses, tuberculosis, 

 etc., that this must necessarily be the case in cancerous tumors. We can, however, 

 say that if parasites play a role in cancer, these parasites must be of an entirely 

 different sort from those, because they must bear the most intimate relationship 

 to the essential cancer cells. I feel that it is not impossible that an intracellular 

 parasite plays a part here, but it cannot possibly play an independent part; it 

 cannot possibly be the decisive element in the tumor; it cannot determine the 

 nature and character of the tumor, for the cells alone do this. 



I consider the existence of such parasites not impossible ; but what can be 

 done to show their presence? 



Experiments to demonstrate the inoculability of tumors from one individual 

 to another show nothing in this regard. For this is nothing but the transplanta- 

 tion of tissue to another individual. Periosteum transplanted to another animal 

 is able to grow in its new host and to form cartilage and bone; or to take a more 

 familiar example, epidermis cells planted upon the surface of a wound of another 

 individual may assume an extreme activity. Successful inoculation of tumors is 

 in no way different. Here it is nothing else than the production of a secondary 

 tumor, or metastasis in a second individual. Parasites are not required. 



If we had only succeeded in producing tuberculosis by means of tuberculous 

 tissue, the truth could never have been brought that tuberculosis was produced 

 by tubercle bacilli. The parasitic nature of tuberculosis was only permanently 

 and definitely established by the fact that by the inoculation of absolutely clean 

 tubercle bacilli, free from all remains of tissue, the same result could be obtained 

 as by tuberculous tissue, only by the fact that absolutely pure bacilli always 

 produce primary tuberculosis in proper animals. We cannot show the etiologic 

 nature of cancer or its power of transplantation by producing new secondary 

 cancers even in another individual but only by producing primary tumors. Until 

 that succeeds, and by pure, artificially grown organisms, the parasitic nature of 

 cancer has not been proven. 



Another question remains to be considered, viz., whether the present condition 

 of our knowledge demands the assumption of a parasitic origin for cancer. Long 

 before the parasites of infectious diseases were discovered, there could be no 

 doubt that such must exist; and even to-day there are diseases, I need mention 

 only syphilis, in which we do not know the parasitic cause, but cannot doubt that 

 it must be present. Is the condition similar as regards cancer? 



The fact which is to be explained in cancer is the limitless, the heterotopic 

 growth of epithelial cells. I will not enter further into the question of how this 

 may be explained than to state that there are many possible explanations and 



