IMMUNITY, 69 



CHAPTER XIY. 



IMMUNITY 



THE natural or acquired power of resistance to bacterial 

 influences is called immunity. 



Natural. As we have mentioned before, certain animals are 

 naturally not acted upon by bacteria that affect other animals. 

 We say the animal or person is immune by nature. 



Acquired, But immunity can be acquired by various means. 

 We know that one case of smallpox usually protects against 

 other attacks and so with morbilla and scarlatina. This is 

 through disease. 



Acclimatization Immunity. Various diseases, which strangers 

 to a climate become 'affected with, do not trouble the natives. 



Artificial Immunity. By the attenuated virus, as with anthrax. 



Inoculations with sterilized cultures, the germs being destroyed. 

 Even certain chemical substances when injected give immunity 

 from certain germs, and when albumen prepared in certain ways 

 was injected, immunity also obtained. 



Inoculations intravenously with greaily diluted virulent cultures 

 give immunity. The various theories which have been made to 

 explain the phenomena of immunity are all unsatisfactory. Some 

 say tnat a first attack destroys the agents which are necessary for 

 the disease to arise. Others say that certain bacterial products 

 remain in the body, and prevent a return of the diseases act as 

 guards. Some recently claim that the soil is rendered unfit for 

 the further development of the bacteria, after injection of some 

 of the active principles of the bacterium. Some place it in 

 the blood of the animals, it exerting a direct germicidal action. 



Alexins. The latest researches place the power of immunity 

 in a certain principle called alexine (oMlsii/, to defend), which has 

 its residence in the serum of the blood and tissues. This principle 

 destroys the bacilli, and they in dying, give out proteids, causing 

 the leucocytes to wander towards these proteids and digest the 

 dying bacilli. The alexins are supposed to be produced by cells 

 containing eosinephile granules. 



