LYSINS, .AGGLUTININS, PRECIPITINS, ETC. 225 



the bacteriolytic digestive power of such immune serum, when destroyed 

 by heating, or after being attenuated by time, could be restored by the 

 addition to it of small quantities of normal blood serum. It could, in 

 other words, be "reactivated" by normal serum. From this obser- 

 vation Bordet drew the conclusion that the bactericidal or bacteriolytic 

 action of the serum depended upon two distinct substances. The one 

 present in normal serum and thermolabile, he conceived to be identical 

 with Buchner's alexin. The other, more stable, produced or at least 

 increased in the serum by the process of immunization, he called the 

 "sensitizing substance." This substance, he believed, acting upon 

 the bacterial cells, rendered them vulnerable to the action of the alexin. 

 Without the previous preparatory action of the " sensitizing substance " 

 the alexin was unable to act. Without the co-operation of alexin, the 

 "sensitizing substance " produced no visible effects. 



Bordet's interpretation of the phenomenon of lysis differs essentially 

 from that of Ehrlich, in that both active serum components are con- 

 ceived by him, though independent, to act directly upon the bacterial 

 cell. A few years later, Bordet was able to show that exactly analogous 

 conditions governed the phenomenon known as "hemolysis" or dis- 

 integration of red blood cells. 



It had been known for many years that in the transfusion of blood 

 from an animal of one species into an animal of another species, in- 

 jury was done to the red corpuscles which were introduced. Observed 

 in the test tube, the red cells in the heterologous serum were seen to 

 give up their hemoglobin in the fluid, the mixture taking on the red 

 transparency characteristic of what is known as " laked " blood. Buch- 

 ner,' in his alexin studies, had shown that the blood-cell destroying 

 action of the normal serum was subject to the same laws as the bac- 

 tericidal power of similar serum, in that it was destroyed by heating, 

 and he assumed that both the' bacteriolytic and the hemolytic action 

 of normal serum were due to the same "alexin." Metchnikoff,^ more- 

 over, had pointed out the striking analogy between the two phenomena 

 as early as 1889. 



Bordet ^ now observed that the blood serum of guinea-pigs previously 

 treated with the defibrinated blood of rabbits developed marked powers 

 of dissolving rabbits' corpuscles, and that this hemolytic action could 



' Buchner, Arch. f. Hyg., xvii, 1893; Waremberg, Arch, d. m^d. exper., 1891, 

 2 Metchnihoff, Ann. de I'inst. Pasteur, 1889. 

 ' Bordet, Ann. de Tinst, Pasteur, t, xii, 1898, 



