192 PROTISTS AND DISEASE 



nuclear parasites are almost identical with stages of the 

 nucleolus of the thistle-Synchytrium, Fig. 23 ; d and e. 



In its earlier phases the sarcoma-parasite follows the 

 course of Plassomyxa contagiosa, differing from the latter as 

 also do Cytoryctes variolae and C. luis in that the stages 

 ending in subdivision occur in the host-tissues. 



This instance of a typical sarcoma proves Cohnheim to 

 have erred in narrowing the term tumour to exclude infective 

 granulomatous growths. 



Epithelial cancer. To illustrate this variety of malignant 

 tumour I will dwell chiefly on that which arises in stratified 

 squamous epithelium because, as if from synchytrian inheri- 

 tance, in this habitat the parasites assume their later stages 

 in greater completeness than in less coherent epithelia ; but 

 in all spontaneous cancers the pathogenesis is practically 

 the same. With regard to the original site of the parasites 

 in this and other spontaneous cancers it is intranuclear like 

 that of the parasites in the mammary sarcoma described 

 above. 



Intranuclear parasites as seen in a section of a breast- 

 cancer are shown in Fig. 56. 



The first cancer in which I recognised parasites akin to 

 Sporozoa was a growth arising in that part of the nasal 

 septum which is covered by skin : it had been removed by 

 Scanes Spicer from a man aged 82. The moisture of the 

 cavity in which the tumour grew had allowed parasites, 

 which are usually distorted and disguised in the cell-nests 



