XIX] PROTOZOA CAUSING DISEASE 5" 



of the elements of the problem that has to be dealt with ; 

 indeed, to every one who has devoted any considerable 

 amount of attention to pathological histology in general, and 

 to the changes of the epithelium in health and disease in 

 particular, it will be clear that insistence on this necessity 

 is by no means uncalled for. By going carefully over the 

 descriptions and illustrations of the "cancer parasites" put 

 forward by different observers, it is quite obvious that a 

 considerable number of them have thought it sufficient, 

 having made a few sections of cancer material, and having 

 stained and mounted them, to at once declare without 

 hesitation — and regardless of the histology, normal and 

 pathological, of epithelium — that such-and-such a particle 

 or corpuscle present in the substance of the epithelial cell 

 or in its nucleus is a parasite. As to this, I illustrate my 

 meaning as follows : — 



Podwyssozki and Sawtschenko published in the 

 Centralblatt f. Bakt. imd Parasit. vol. xi., Nos. i6, 17, and 

 18, a paper on cancer psorosperms, and they add two 

 coloured plates (Plates VII. and VIII.) illustrating the 

 presence of the alleged sporozoa within and between the 

 epithelial cells. Now, any one who, after staining them, has 

 examined sections of well-preserved epithelial structures, 

 growing and proliferating under normal and under patho- 

 logical conditions, will recognise in the figures given by 

 these authors appearances very commonly met with : viz., 

 bodies, variously shaped and variously sized, contained 

 within the cells ; bodies, indeed, which take the stain 

 differently from the typical nucleus of the epithelial cell. 

 These bodies are commonly and justly considered to be 

 derivatives of the nuclear substance, particularly of that 

 portion commonly called chromatin. Appearances such as 

 are shown by the authors in their Figures 1-7, n-i.S, 16-20, 



