CHAPTER XXIX. 

 RECEPTORS OF THE THIRD ORDER. 



CYTOLYSINS. 



Before Koch definitely proved bacteria capable of 

 causing disease, several physiologists had noted that the 

 red corpuscles of certain animals were destroyed by the blood 

 of other animals (Creite, 1869, Landois, 1875), and Traube 

 and Gescheidel had shown that freshly drawn blood de- 

 stroys bacteria (1874). It was not until about ten years 

 afterward that this action of the blood began to be investi- 

 gated in connection with the subject of immunity. Von 

 Fodor (1885) showed that saprophytic bacteria injected into 

 the blood are rapidly destroyed. Fliigge and his pupils, 

 especially Nuttall, in combating Metchnikoff's theory of 

 phagocytosis, announced in 1883, studied the action of the 

 blood on bacteria and showed its destructive effect (1885-87). 

 Nuttall also showed that the blood lost this power if heated 

 to 56°. Buchner (1889) gave the name "alexin" (from the 

 Greek ''to ward off") to the destroying substance and showed 

 that the substance was present in the blood serum as well as 

 in the whole blood, and that when the serum lost its power 

 to dissolve, this could be restored by adding fresh blood. 

 Pfeiffer (1894) showed that the destructive power of the 

 blood of animals immunized against bacteria (cholera and 

 typhoid) was markedly specific for the bacteria used. He 

 introduced a mixture of the blood and the bacteria into the 

 abdominal cavity of the immunized animal or of a normal 

 one of the same species and noted the rapid solution of the 

 bacteria by withdrawing portions of the peritoneal fluid and 

 examining them ("Pfeiffer's phenomenon"). Belfanti and 

 Carbone, and especially Bordet (1898), showed the specific 

 dissolving action of the serum of one animal on the blood 

 corpuscles of another animal with which it had been injected. 



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