348 THE CAUSATION OF DISEASE. 



through the power of one tissue to alter the cell-E of another, 

 in which case the chief share of causation would belong to S — 

 that is, to the body, and not to any agent independently of the 

 body : the growth would, in short, be due to an innate tendency 

 of the body to undergo the change independently of external 

 nocuous agent. But is the body capable of affording the 

 necessary E ? By modifications of blood-supply and nerve 

 influence, the nutrition of a part may be influenced, and thus 

 we may get hypertrophy, atrophy, or degenerative changes, 

 but I know of no nutritive change thus wrought which is at 

 all akin to the malignant change. In derangement of the 

 nervous system, for instance, rashes, sloughings, and many 

 other changes may occur through modification of cell-E ; but 

 these differ from the malignant changes in several important 

 particulars. In the first place, a malignant tumour starts 

 from a microscopic centre, and spreads thence, while . or- 

 dinary "trophic" and degenerative changes start more or less 

 evenly throughout the whole of the affected area ; then again, 

 in trophic changes, there is, for the most part, diminution in 

 the bulk of the affected part ; further, in the case of secondary 

 growths we can eliminate any such trophic influence. 



A study of the mode of growth of the malignant tumours 

 is, I say, strongly suggestive of a sudden change in the cell-E 

 of the affected parts. There is nothing to be said in favour of 

 the growths being due to an innate structural tendency, 

 independently of a localized specific mal-environment, and there 

 are several arguments against this view. If we assume the 

 chief element of causation to reside in S, we must narrow 

 down the primarily faulty S to a very minute area — to an 

 area, indeed, of microscopic proportions. Then, again, all 

 acknowledge a sudden .change of E in the case of the 

 secondary tumours : these never occur from an innate ten- 

 dency of the affected tissue to undergo the malignant change, 

 independently of altered E. Finally, the change is retrogres- 

 sive ; there is not evolution, but dissolution, and one patch of 

 tissue never takes on a dissolutionary change independently of 

 altered cell-E. I shall have shortly to revert to this subject 

 of retrogression. 



The theory that malignant growths are developed from 



