766 



PARASITES IN TUMOURS 



On examining the preparation under the microscope, in addition to normal 

 epithelial cells a number of cells distended with Klossia will be seen (fig. 369). 

 The parasite passes through all the stages of its life history in 

 the same cell : the nucleus of the infected cell is often consider- 

 ably hypertrophied (up to 60 times its natural size), and later 

 when the coccidium has attained large dimensions the 

 nucleus degenerates and atrophies. 



Within the oocyst several sporocysts are formed : each sporo- 

 cyst gives rise to four sporozoites and a residuum. When the 

 sporozoi'tes are set free they infect other epithelial cells where 

 they form schizonts, which pass through the ordinary processes 

 of schizogony. 



The following genera, which include no human parasite among 

 their numerous species, may be mentioned : Cyclospora, Barrouxia, 

 Adelea, Legerella. 



FIG. 369. 

 Klossia helicina. 

 Kidney cell of 

 Helix hortensis 

 containing three 



SECTION III. PARASITES IN TUMOURS. 

 1. Coccidia. 



The discovery a few years ago of structures, which were said to 

 bear a striking resemblance to the coccidia, in certain epithelial 

 is situated near neoplasms seemed to afford a scientific basis for the parasitic theory 

 the narrow end o f malignant new growths : and within a short space of time dis- 

 (AfterBafbianLJ coveries of protozoa in epithelial tumours were reported from all 

 quarters. 



The accounts of the numerous apparently successful investigations which were 

 at once set on foot on receipt of these reports only serve to show the errors into 

 which one may fall in interpreting observed appearances : the result is that these 

 researches are discredited and that the majority of histologists have now discarded 

 the theory of the coccidial origin of new growths. 



Many observers have succeeded in inoculating malignant new growths from one 

 animal into another of the same species and even into animals of different species, 

 these experiments being especially successful when a mouse cancer is inoculated 

 into other mice. But these inoculations result not in a true infection but merely 

 in a graft of cancer cells, and the growth which follows a successful inoculation is 

 in Jensen's words " a true culture of cancer cells." The more important of the 

 appearances which have been described as parasites of new growths will be here 

 briefly passed in review (vide also pp. 707, 735, 839). 



I. Neisser, in 1888, affirmed the parasitic nature of Molluscum contagiosum or 

 Acne varioliforme : and described certain peculiar oviform structures which he 

 regarded as Coccidia. These structures however are merely cells undergoing hyaline 

 degeneration. 



In sections stained with Ranvier's picro- carmine it can be seen that the changes 

 in the cells increase progressively from the centre to the surface of the growth. The 

 nuclei distinctly visible in the deeper layers are less conspicuous in the parts nearer 

 the surface : the section which is stained yellowish pink in the centre becomes more 

 and more yellow as the periphery is approached : the cells themselves are more and 

 more infiltrated with an hyaline substance which finally occupies the whole of the 

 cell body including the nucleus : towards the centre the hyaline oval cells are packed 

 closely one against another and are surrounded by a filamentous network containing 

 granules of eleidine. No indication of the structures described and no oviform 

 parasitic bodies can however be made out, and the only changes visible are the 

 changes in the cells undergoing keratinization. 



EL. Darier, Malassez, and Wickham have described certain appearances in psoro- 

 spermosis follicularis and in Pagefs disease of the nipple which, being always situated 

 within the neoplastic cells, they took to be encysted coccidia. 



The structures described by these authors are not parasites, but cells of the 

 epidermis derived from the Malpighian layer which after undergoing certain changes 

 analogous to that of normal keratinization and becoming rolled up and cut off from 



