Contagious (^Zymotic) Diseases. 5 



is not possible with the simple chemical product in solution, 

 which has neither life nor power of self propagation. When, 

 therefore, we aim at the complete extinction of a disease and its 

 infection, and when this can be effected equally well by the use 

 of the simple chemical products, this is much to be preferred to 

 the use of live microbes however much they may be enfeebled. 



In seeking a scientific explanation of immunization, many sub- 

 sidiary factors and complex conditions have been discovered, and 

 on these have been based ingenious theories which must be men- 

 tioned. 



Phagocytosis i^phagein, to eat, cytos, a cell) is the process in which 

 cells possessed of amoeboid movement, lymphoid and neutrophile 

 leucocytes, etc., flow out into arms (pseudopodia) which enclose 

 solids that they digest as food, and among these the invading 

 pathogenic microbes ( MetchnikofE) . When the englobed microbes 

 are not too numerous in a cell or too toxic, they are themselves 

 dissolved and digested and their destructive powers arrested. On 

 the other hand, the cells often perish and even become for a 

 time centres for the culture and encrease of the microbes within 

 them. This is well shown in the great destruction of the blood 

 globules in Texas fever and other affections. 



The defensive products of the phagocytes include an enzyme 

 (ferment) or cytase which dissolves the microbe or other body 

 on which it operates : and a cytotoxin (Jeucotoxin) which poisons 

 or enfeebles the invading organism so that it may be less able to 

 produce defensive secretions and protect itself. These defensive 

 products of the cell are especially attributable to the lymphocytes 

 whether in the blood or the great lymphatic system, to the 

 amoeboid epithelium of the capillaries, and to the wandering 

 lymphocytes, but also in part to the red blood globules, and it is 

 presumed the tissue cells when set free in inflammation, and 

 endowed anew with amoeboid movement. The defensive pro- 

 ducts pass out of the cells into the surrounding serum endowing 

 that with defensive qualities similar in kind. Hence the principle 

 of serum therapy. 



Hesmolysins are enzymes that cause solution and destruction 

 of blood globules. Injection intravenously, intraperitoneally, or 

 subcutaneously, into a guineapig, horse or other animal of the 

 defibrinated blood or blood serum of the rabbit, determines in 



