THE CAUSATION OF DISEASE. I 5 



We must very carefully observe that the external material 

 conditions can in no way be excluded from the field of causation. 

 They are as necessary as the internal material conditions. In 

 other words, the environment takes as large a share in the 

 vital processes as the cell itself. 



Life, then, being an interaction of cell and cell-environment, 

 disease, which is a peculiar mode of life, must have a similar 

 causation. Assuming an ideal standard of healthful life — 

 which is easy enough to conceive but most difficult to define * 

 — we may speak of disease as an abnormal mode of life. We 

 arrive, therefore, at this important principle : all disease depends 

 upon either (i) peculiarity of cell- or tissue-structure; (2) pecu- 

 liarity of cell-environment ; or, finally, (3) peculiarity of both. 

 If a cell be perfectly fashioned as regards the kind of its 

 component atoms, the arrangement of these into molecules, 

 and the disposition of the latter among themselves ; and, if, 

 moreover, the environment be a fit one, the vital processes 

 must of necessity proceed healthily. The cell is endowed 

 with certain powers, the outcome of structure, and, like a wound- 

 up clock, must run through its course of action. This follows 

 from the law of causation : given the same conditions, the same 

 results must always follow. But if, on the other hand, the 

 cell-structure be abnormal, or if its environment be unfitted to 

 its proper working, the vital processes will no longer go on 

 normally : there will be, not health, but disease. 



Disease, then, having two sides — (1) cell-structure, (2) cell- 

 other." Further, the Duke of Argyll remarks: "Let us never forget that 

 life, as we know it here below, is the antecedent or the cause of organization, 

 and not its product ; that the peculiar combinations of matter, which are the 

 homes and the abodes of life, are prepared and shaped under the control and 

 guidance of that mysterious power which we know as vitality ; and that no 

 discovery of science has ever been able to reduce it to a lower level, or to 

 identify it with any purely material force." Quatrefages speaks in a like 

 strain : " Living beings are heavy, and therefore subject to gravitation ; they 



are the seat of numerous and various physico-chemical phenomena But 



these phenomena are under the influence of a notlier force ( = Life)." It is 

 worthy of note that both of these latter authors are anti-Darwinists. This 

 question has, I hold, been permanently set at rest by the lucid writings of 

 Huxley. 



* The question of ideal normality of structure and environment will be 

 considered in a future chapter (Part II.). 



