Contagious and Epizootic Diseases. o3 



guzzler, or the arsenic-eater. Equally possible is it, by an 

 excessive dose of a specific disease-poison, to lay the best 

 protected system under the fatal influence of that disease. 

 There is no such thing as conferring absolute immunity. 

 Hence the occasional occurrence of a second attack of small- 

 pox, or other plague, on occasions when the disease has be- 

 come unusually virulent, or acts on a specially depressed 

 system. 



But this cannot be the whole measure of the antagonism. 

 "Were it to rest here the multiplication of the disease-germ 

 might be as great as before, the system might become satu- 

 rated with these germs, and trouble would inevitably come 

 from the exhaustion of the blood and animal fluids of their 

 oxygen, the blocking of capillaries, etc. The germs and their 

 products would tend to increase till the vital resistance was 

 overcome, and a fatal result might ensue. The important 

 feature of the resistance is that it prevents the survival and 

 increase of the germs introduced into the body. In the pro- 

 tected animal system, therefore, there is not simply a vital 

 insusceptibility of the cells and nuclei to the action of tlie 

 chemical products of disease, but there is in addition an 

 active antagonism between the living animal cell and the 

 living disease-germ. There is a certain similarity between 

 the bacterial ferment and the plastic animal cell, in that both 

 are engaged in taking in and using up organic matter for 

 their own nourishment, or, in the case of the animal cell, for 

 the building up -of tissue. Each finds in the other organic 

 matter by the devouring of which it can support its own 

 life. Each would feed upon the other but for the vital re- 

 sistance offered by its antagonist. If one is killed, or has its 

 vitality depressed as compared with the other, the latter will 

 destroy and devour it. If, then, tlie nuclei of the tissues 

 liave had their vitality lowered by the action for the first 

 time of the poisonous chemical products of the disease-germ, 

 they meet the attacks of that germ at a disadvantage, for a 



