CARCINOMATA. 455 



In the human gall-bladder we only meet with excessively 

 minute and insignificant papillomata. On the other hand, 

 Virchow has placed upon record the case of a cow, whose gall- 

 bladder he examined ; its thickened walls " were beset with such 

 multitudes of partly villous, partly cylindrical, solid out- 

 growths, that the mucous surface over a certain area seemed 

 to have entirely disappeared." 



§ 392. The relations of these papillomata to epitlielial cancer 

 of the mucous membrane, are both interesting and important. 

 Not only has it been show^n that a papilloma maj^ pass into an 

 epithelioma, and that an epithelioma may be secondarily com- 

 plicated by papillary proliferation from the edges and base of the 

 ulcer, but it has been repeatedly asserted that the mucous 

 membrane over a cancer which is forming in the submucous 

 tissue, is prone to become the seat of papillary growth. For my 

 own part, I have never observed anything of the kind, and I 

 cannot therefore express any opinion concerning the intimate 

 connexion of these two phenomena. Virchoiu regards the de- 

 velopment of the papillomata as a simply hyperplastic change 

 to begin with, excited by the irritation of the adjoining cancerous 

 formation ; the possibility of its conversion into a true villous 

 CANCER only beginning, when the carcinoma is propagated by 

 continuous infiltration from below, to the connective tissue of 

 the papillae. He goes on to say, that the stomach and urinary 

 bladder are the chief seats of these true villous cancers, which 

 are probably identical with our own columnar epitheliomata. 



2. Carcinoinata. 



§ 398. The mucous surfaces, lined as they are with epithe- 

 lium, are everywhere disposed to the production of epithelio- 

 mata ; to that of glandular cancer only in so far as they happen 

 to contain open glands. To this latter circumstance must be 

 ascribed the striking differences between the average liability 

 of various regions of the mucous tract to cancer. Moreover, the 

 epithelial form seems to prefer the points of junction between 

 the several divisions of the mucous tract ; this is mainly owing 

 to the pre-eminent exposure of such localities to mechanical 

 irritation of some sort, which need not necessarily be abnormal. 



§ 394. Starting from those orifices of the mucous system 



