1 8 THE CAUSATION OF DISEASE. 



activity is checked by the products of its own cell-action — 

 by alcohol for instance. Thus we see that the E controls cell 

 activity, a rich food-supply hurrying on the vital process, while 

 the presence of certain poisonous substances has the opposite 

 effect. So much for unicellular organisms. 



The Internal- Cell-Environment. — I have hitherto, for the 

 sake of simplicity, spoken chiefly of single unit cells — for I 

 wish to proceed from the simple to the more complex — but 

 it is now necessary to remember that the tissues of a complex 



Fig. 2. 



Cell 



Lymphatic. 



Fluid Plasma in which 

 the cells lie bathed. 



organism consist of many such cells. Each cell is fixed in 

 its proper place by a connecting tissue substance, and each 

 (excepting those lying upon the surfaces) dwells in a tiny 

 chamber, where it lies bathed in a nutrient fluid, which 

 percolates the wall of the capillary blood-vessel, and after 

 passing into the cell-chambers, escapes by the lymphatic 

 vessels leading out of them. Every cell is thus, like the 

 amceba, bathed in a nutrient fluid, from which it derives its 

 food, and to which it returns its refuse. (See Fig. 2.) 



The life of a complex organism may be defined as the sum 

 of all those interactions luhich take place between the various 

 cells constituting the organism and their several environments. 



Much that is highly interesting and instructive might be 

 written on the part played by individual cell-E in the processes 

 of hypertrophy, degeneration, and development, but my re- 

 marks on this head can only be few. In treating of the 

 factors which determine structure, I shall attempt to show how 

 important is the role played by E. For the present I will only 



