XIX] PROTOZOA CAUSING DISEASE 523 



large amoeba that has thrown out a long stalk, and that 

 when the amoeba, after the nature of amoebse, divides it 

 gives origin to smaller nucleated protoplasmic masses. If 

 only the latter were present in the sections, it would, owing 

 to their special staining and their intracellular position, not 

 be difficult to mistake them for epithelial cells or leucocytes ; 

 but the presence of the large pedunculated knobbed masses 

 is of the utmost importance as proving that we are dealing 

 with something quite different from either epithelial cells or 

 leucocytes. 



I have searched for these pedunculated amoeba in a 

 large number of carcinomata ; but, excepting a single case 

 of carcinoma of the oesophagus, I have not come across 

 them. As already stated, however, Korotneff has in this 

 respect been more fortunate. 



To sum up, then, we have to exclude from the evidence 

 adduced by the various authors, as indicating cancer 

 parasites, the following bodies : — 



{a) Nucleated epithelial cells which have undergone a 

 kerato-hyaline change. These are observable as spheroidal 

 or oval corpuscles, generally situated away from the deepest 

 epithelial cells : that is, from the cells immediately in con- 

 tact with the connective tissue matrix. They are of about 

 the size of ordinary epithelial cells, stain like keratin of the 

 superficial cells, and possess a relatively small deeply stained 

 shrunken nucleus, such as is found in many other examples 

 of chemically or acutely inflamed epithelium. 



{d) Spherical transparent cells with one, two, or more 

 nuclei, which in aspect, size, nuclei, and in their mode of 

 staining, cannot be distinguished from ordinary leucocytes. 

 They are found between the epithelial cells, or have im- 

 migrated into the substance of the latter — as in the case 

 of vacuolated epithelial cells enclosing leucocytes. This 



