172 THE CAUSATION OF DISEASE. 



to use this symbolical method in the case of injuries, and, there- 

 fore, I will not attempt to show how it could be rendered 

 accurate. I am, indeed, not ambitious enough to hope to reduce 

 to scientific precision this method of valuing the relative shares 

 taken by S and E in the causation of particular diseases. It is 

 obviously impossible to do so. I have used it simply as an in- 

 strument of thought, and it may perhaps be occasionally useful 

 in studying the causation of a particular disease, by presenting 

 the actual state of things to the mind in a more or less tangible 

 form. 



In the light of our present position, let us examine the 

 following statement made by Dr. Kussell Reynolds in the intro- 

 duction to his " System of Medicine." 



In speaking of " predisposing causes " of disease, he reminds 

 us that heredity, sex, age, constitutional peculiarity, congenital or 

 acquired, are generally included among them. We have seen 

 what a potent part heredity takes in determining S, and that 

 age and sex necessarily fall under the same principle. More- 

 over, it is obvious, from former remarks, that " constitutional 

 peculiarity/' which is nothing else than structural peculiarity, is 

 either hereditary or acquired ( = due to E). According to our 

 manner of viewing it, it must be one or the other, for we have 

 seen that no peculiarity can arise spontaneously ; if not due to 

 heredity, it must be due to E, a congenital peculiarity being 

 either hereditary or the result of peculiar ante-partem E. 



Now to proceed to Dr. Reynolds' statement : "In regard 

 to heredity-taint and constitutional peculiarity, we must admit 

 that they are in reality diseases " (my own italics). Later 

 on he affirms them to be part of the disease itself. Thus, a 

 " man of tuberculous family, and with latent tubercle, was 

 yesterday apparently well, but he was exposed to cold, and to- 

 day he has tubercular pneumonia. This constitutional state 

 predisposed him to the evil which the exposure excited into 

 activity. It was not a cause of the disease that uxcs there, hut 

 an integral part of the affection'' 



We have already seen that we cannot separate S from 

 causation, seeing that disease is a peculiar inter-action of S 

 and E. But, whether we are justified in calling any pecu- 



