344 THE CAUSATION" OF DISEASE. 



Ss + E will represent the causation of cancer in any given 

 case. Observe the importance of s. It might so happen in a 

 particular case that Ss 4- this same E would not cause the dis- 

 ease, even though the S were the same as in the first case. 

 The s, which represents the moulding of the body through 

 a series of years, might have been a totally different quantity 

 from that in the first case, and one preventing the specific E 

 from working its dire effect upon the body. 



Let it ever be borne in mind that we can never exclude S 

 from the causation of disease. How is it possible to do so, 

 seeing that disease is an abnormal inter-action of S and E ? 

 Occasionally, for practical purposes, we may. When a man 

 breaks his leg from a fall, we do not say it is his leg that 

 is the cause ; but if two healthy individuals be equally exposed 

 to the scarlatina poison, and only one contracts the disease, it 

 is evident that it is impracticable to exclude the S from a share 

 in causation. 



One word on what may be termed the potentiality of S. The 

 tissues are endowed with a vast number of potentialities — that 

 is, slumbering possibilities — dormant states needing but a 

 fitting E to awaken them into actual being. This subject 

 has not, in my belief, received its proper attention from 

 pathologists. Whatever be the evil factor in the causation of 

 malignant growths, it is to be noted that the affected tis- 

 sues must possess the potential power of taking on the par- 

 ticular morbid action, and in the cancers the structure of the 

 growth is by no means simple. The power of thus growing 

 must have been previously locked up in the affected tissue, so 

 that even if we find a parasite to be the exciting cause of 

 cancer, we must remember that the power of growing in this 

 peculiar way belongs to the body. 



With these remarks on the Causation of Disease in general, 

 let us now proceed to discuss the causation of cancer in par- 

 ticular. 



The question — Does the tumour originate in a multiplication 

 of the few cells initially constituting it, or in a transformation 

 of the affected tissues ? — must first engage our attention. It 

 may obviously originate in either, or in both, of these ways. All 



