mm 



MARTIN — DISCUSSION ON CARCINOMA. 



695 



satisfactorily the etiological relationship. As in these diseases, so too 

 in carcinoma, where our knowledge is likewise very limited so far a»s 

 the true cause is concerned, we are scarcely justified in discarding 

 the theory of a parasitic origin till definite proofs to the contrary are 

 established. 



The customary classification of tumours, in so far as it does not 

 consider their etiology, has been formed entirely on a basis of con- 

 venience in their nomenclature. The histological structures alone are 

 taken as a means of differentiation beoween all the different types of 

 neoplasms quite regardless of the cause inducing their growth. The 

 distinction likewise between benign and malignant tumours is as 

 much a clinical as a pathological differentiation and conveys no idea 

 of their respective etiology, and one of the reasons is apparent. At 

 the time when Virchow's classical work on cellular pathology appeared, 

 parasites played absolutely no role in the study of pathological pro- 

 cesses, and as the nature of tumours was then even more in doubt 

 than now his desire was to formulate merely some convenient plan of 

 nomenclature. 



It is here that the first difficulty arises, for the merest superficial 

 study of benign and malignant tumours suggests at once a difference 

 so great as to render it more than likely that their respective causes 

 are equally distinct. There are few pathologists to-day who ascribe 

 the formation of malignant tumours to an overgrowth of embryonic 

 cell remains, as suggested by Cohnheim for the origin of benign 

 tumours, and the reason is obvious. When a tissue in its overgrowth 

 ceases to remain local, ceases to retain its simple structure and regu- 

 larity of outline, but tends to be distributed throughout distiint 

 portions of the body, there is at once suggested some special kind of 

 stimulus, some unusual cause for such an irregular mode of procedure 

 and extension of cells. The cause can hardly be identical with that 

 for other more benign tumours, else one would surely get at some 

 time or other an extension by metastases of lipomata, fibromata, etc. 

 This, however, never does occur with the same invasive propensities, 

 and there is at no time a paramount tendency to extension even 

 locally. Some would explain this by the greater regenerative and 

 proliferative power of epithelial cells over any other kind of tissue. 

 While, howev6r, such is the case, it is but a poor explanation of the 

 atypical character of the growths in malignant tumours. Rapidity of 

 growth alone can certainly not explain it, for whenever the epithelial 

 growths extend rapidly it is because they find paths of small resist- 

 ance, i. e., the looser tissues and the surfaces, forming thus cauliflower 

 excrescences, and so forth. It is rather where their growth is slow 



