CHAPTER XXIX. 

 RECEPTORS OF THE THIRD ORDER. 



CYTOLYSINS. 



Before Koch definitely proved bacteria capable of caus- 

 ing disease several physiologists had noted that the red cor- 

 puscles 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 destroys 

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

 that this action of the blood began to be investigated 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 phago- 

 cytosis, announced in 1883, studied the action of the blood 

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

 Xuttall 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 exam- 

 ining them ("Pfeiffer's phenomenon"). Belfanti and Car- 

 bone and especially Bordet (1898) showed the specific dis- 

 solving action of the serum of one animal on the blood cor- 



