CHAPTER III 

 ANAPHYLAXIS 



When the serum of one species of animal is injected 

 into an individual of another species, antibodies are 

 formed, as has already been described. But. in addi- 

 tion to this formation of antibodies, or as a part of 

 the process, changes take place in the infected animal ; 

 by these it is rendered peculiarly sensitive to a 

 further injection of the same kind of serum. Symp- 

 toms of severe constitutional disturbances, and often 

 even death, may ensue upon a second injection. 

 Thus, if an animal receives an intraperitoneal injec- 

 tion of horse serum it suffers no ill effects, but if the 

 injection is repeated in about twelve days' time, it is 

 liable to become seriously ill, with symptoms of 

 collapse, bloody urine and faeces, dyspnoea, and 

 convulsions, and may die rapidly or instantaneously. 

 The phenomenon is known as anaphylaxis. 



This condition is not confined to the use of serum, 

 but is established when proteins of a wide range are 

 employed. 



This hypersensibility does not develop immediately, 

 but only after the lapse of a varying interval, generally 

 eight to ten days, varying with the protein used and 



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