Vol. L February, 1926 No. 2 



BIOLOGICAL BULLETIN 



THE PRECIPITIN REACTION IN THE STUDY OF 

 ANIMAL RELATIONSHIPS. 



ALAN ARTHUR BOYDEN, 

 ZOOLOGICAL LABORATORY, UNIVERSITY OF WISCONSIN. 



GENERAL HISTORICAL INTRODUCTION. 



The precipitin reaction was discovered by Rudolph Kraus in 

 1897. Having injected a goat with sterile cholera culture 

 filtrates, he found that the blood serum of the goat had come to 

 possess the property of causing a precipitate to appear when it 

 was mixed with perfectly clear solutions of cholera culture 

 filtrates. Normal goat serum, of course, caused no such pre- 

 cipitate. Furthermore, the serum of the goat injected with 

 cholera filtrates (cholera antiserum) caused no precipitate when 

 mixed with bacterial filtrates other than cholera. Similar results 

 were obtained when typhoid and plague culture filtrates were 

 used for inoculation. In these cases typhoid antiserum caused a 

 precipitate only in typhoid filtrates and plague antiserum only in 

 plague filtrates. The reaction was therefore specific in that 

 a precipitate occurred only when an antiserum was mixed with 

 a filtrate of the particular kind of bacteria used for immunization. 

 The substances developed in the blood serum of the immunized 

 animal were called "precipitins" and from them the reaction 

 got its name. The materials which were injected into animals 

 for the purpose of inducing precipitin formation were called 

 " precipitinogens." 



The precipitin reaction became of general biological significance 



two years later when Bordet (1899) and Tchistovitch (1899) 



independently found that proteins other than bacterial could 



act as precipitinogens, i.e., could induce the formation of pre- 



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