i IS PROTOZOA AND DISEASE 



diseases in human tissues, that such cell-forms as those depicted in 

 Fig. 46 can be recognised as parasitic. It is now over thirteen years 

 since I first described my view of a cancer of the nasal fossa, being 

 led to it by a case of cystic ureteritis, in which, after careful study, 

 I came to the conclusion that the disease was caused by protozoa. 

 By further study I extended the view to other cancers and sarcomas, 

 and to syphilis, etc. Every time during these past years that I have 

 re-examined my specimens even when I have tried to take the 

 opposite view I have been confirmed in my view, which is to the 

 effect that the common forms of cancer and sarcoma are caused by 

 more or less local infections by protozoa, and differ from the infec- 

 tive granulomata only in the more intimate character of the 

 parasitism and the more complicated life-history of the parasites.' 



Before deciding that the large free cells, such as those shown in 

 Fig. 46, belong to the same series as the intranuclear bodies that I 

 regard as protozoa, I had duly considered the possibility of their 

 being connective-tissue cells which had become free from the net- 

 work, their protoplasm having assumed a more highly refracting 

 character than is usual in such cells. 



The result of a close examination of all the series of forms and a 

 comparison of them with similar bodies in other tumours led me to 

 the above decision. 



When this sarcoma is compared with those of the breast and 

 testis described above, we find that the small parasitic elements 

 that I have mentioned as occurring in the cells of the myxosarcoma 

 were limited to the cytoplasm ; and if they had an intranuclear 

 stage comparable to that of the corresponding bodies in two sarcomas 

 of the breast and testis, this stage must have been of very short 

 duration, and the parasites must have been undiscernible as some- 

 thing foreign to the cell by the ordinary microscopic examination. 

 Moreover, the tissue-cells of the tumour are very delicate, being 

 merely the connective-tissue cells separated by a gelatinous inter- 

 cellular substance ; and the parasites being of rapid growth, the latter 

 soon escape from the cells ; and so most of them are free. With 

 regard to some of the larger parasites, it is sometimes difficult to 



