23G STUDIES IN IMMUNITY. 



the same alexin that unites with and destroys various cells. In 

 the preceding article with Dr. Gengou we found that various 

 bacteria absorb the alexin which is essential for the destruction 

 of red blood cells or of other bacteria. 



We may mention two other similar experiments. The red spiril- 

 lum, a non-pathogenic organism, is readily destroyed by the serum 

 of a normal guinea-pig, even without the addition of a sensitizer. 

 In each of two tubes is placed 0.2 of a cubic centimeter of fresh 

 hemolytic serum obtained from guinea-pigs immunized against rab- 

 bit blood. To tube "a" 0.3 of a cubic centimeter of guinea-pig 

 blood is added; to tube "b" 0.3 of a cubic centimeter of washed 

 rabbit blood. After a few hours 2 drops of an emulsion of the 

 spirillum are added to each tube and they are placed in the incu- 

 bator. The spirilla are destroyed in tube " a, " in which the guinea- 

 pig corpuscles have remained intact; they remain normal in tube 

 "b" containing hemolyzed rabbit corpuscles. Sensitized hen cor- 

 puscles subsequently added to both tubes are hemolyzed in "a, " 

 but remain intact in "b." Rabbit corpuscles, then, by absorbing 

 the alexin protect two very different cells the spirillum and hen 

 corpuscles. 



In the other experiment we have to deal with a rather peculiar 

 instance. We may ask whether the rabbit alexin that destroys sen- 

 sitized rabbit corpuscles differs from the alexin in the same serum 

 which attacks other species of corpuscles. Experimentally we find 

 that it does not. In each of two tubes "a" and "b" is placed 

 0.2 of a cubic centimeter of washed hen blood; 0.2 of a cubic cen- 

 timeter of fresh normal rabbit serum is then added to each. To 

 tube "a" is then added 0.6 of a cubic centimeter of serum from a 

 rabbit treated with hen blood and heated to 56 degrees. To tube 

 "b" 0.6 of a cubic centimeter of normal rabbit serum (56 degrees) 

 is added. The hen corpuscles are hemolyzed in "a," but remain 

 intact in "b." After a few hours 0.2 of a cubic centimeter of the 

 following mixture is added to each tube: Washed rabbit blood, 

 20 drops; serum of a guinea-pig treated with rabbit blood and 

 heated to 56 degrees, 2 c.c. 



These sensitized corpuscles are destroyed in "b" and remain 

 intact in "a. " 



The fact that a given alexin may attack different cells seems to 



