204 PROTISTS AND DISEASE 



histological methods. Besides visible forms there are doubt- 

 less many in the microhenad phase. Secondary growths 

 are few compared with the number of parasites distributed 

 through the host body. 



Cancer being so common we all at some time or another 

 probably have in us potential cancer-parasites. How do 

 they get into us ? It has been shown above and in Part IV 

 that in old-standing syphilis cancer seems to arise in a 

 peculiar relationship of Cytoryctes luis to the host- cells. A 

 similar relationship between the parasites of measles and 

 other exanthems may possibly produce cancer : these are 

 problems for future investigation. The frequent presence 

 of Karyoryctes in water-protozoa suggests the question 

 whether that or similar plassomyxines may not in some 

 cases become Plassomyxa forma-maligna in man or other 

 mammal. 



Adenoma of the breast, &c. -The cells which line the 

 younger cysts of this common fibre-cystic tumour are 

 swollen, and contain spherical inclusions of colloid-like 

 (pycnoplasson) aspect, the largest on escaping by breaking- 

 up of the cell become a mass of fine granules in the lumen. 

 These and other features point to these bodies being of the 

 same nature as the plassomyxes described above in smallpox, 

 syphilis and cancer. In the latter disease as might be 

 expected the parasites are in a state of more aggressive 

 vitality than in the simpler adenoma, and until the more 

 demonstrative features of the parasites in cancer are accepted 



