462 IMMUNITY. 



ARTIFICIAL IMMUNITY. 



A. Active Immunity i.e., produced in an animal by an 



injection, or by a series of injections, of non-lethal 

 doses of an organism or its toxines. 



1 . By injection of the living organisms. 



(a) Attenuated in various ways. Examples : 



(1) By growing in the presence of oxygen, or 



in a current of air. 



(2) By passing through the tissues of one 



species of animal (becomes attenuated 

 for another species). 



(3) By growing at abnormal temperatures, etc. 



(4) By growing in the presence of weak anti- 



septics, or by injecting the latter along 

 with the organism, etc. 



(b) In a virulent condition, in non-lethal doses. 



2. By injection of the dead organisms. 



3. By injection of filtered bacterial cultures, i.e., toxines ; 



or of chemical substances derived from these. 

 These methods may also be combined in various ways. 



B. Passive Immunity, i.e. t produced in one animal by injec- 



tion of the serum of another animal highly immunised 

 by the methods of A. 



1. By antitoxic serum, i.e., the serum of an animal highly 



immunised against a particular toxine. 



2. By antimicrobic scrum, i.e., the serum of an animal 



highly immunised against a particular organism 

 in the living and virulent condition. 



A. Active Immunity. 



i. By Living Cultures. (a) Attenuated. In the earlier 

 work on immunity in the case of anthrax, chicken cholera, 

 swine plague, etc., the methods consisted in the employ- 



