IMMUNITY. 67 



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. 



The various theories which have been made to explain the 

 phenomena of immunity are all unsatisfactory. Some say that 

 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. 



It has not yet been satisfactorily explained, perhaps, in the 

 late activity of bacteriological workers, some solution of this 

 important question will be arrived at. 



Cure of Infectious Diseases with Bacteria and their Products. 

 Antagonism. It has been known, and is easily demonstrated, 

 that the growth of one bacterium near another results often in 

 the destruction of one, a direct antagonism existing. 



Rabbits suffering with anthrax were injected with large quan- 

 tities of streptococcus of erysipelas (pyogenes), and a cure 

 effected, those not so treated dying. 



Several other diseases have been so treated in animals with 

 interesting results. 



Toxalbumen Injections. When diphtheria is produced in 

 animals, an injection of the toxalbumen of diphtheria will cure 

 the same, and if injected first, diphtheria will not arise. 

 Tetanus has been cured and prevented in a similar manner. 



Tuberculin. Dixon, in 1889, found, by injecting products of 

 tuberculosis cultures in glycerine, that Guinea-pigs so treated, 



