188 STUDIES IN IMMUNITY. 



The presence of the sensitizing substance then increases the herao- 

 lytic power of these sera distinctly. It also increases to a less extent 

 the activity of normal pigeon serum. The normal sera of the 

 hen and the goose are in themselves very hemolytic for rabbit cor- 

 puscles and the addition of sensitizing substance does not appear 

 to increase their properties to any great extent. 



It is to be noted that guinea-pig serum is the one that affects 

 corpuscles subjected to sensitizing substance most actively; this 

 serum is much more effective than rabbit serum. Very large doses 

 of rabbit serum are necessary to destroy sensitized rabbit corpuscles 

 when a small dose of sensitizing substance is used.* An analogous 

 fact has recently been observed by Buchner.f According to this 

 observer bovine red blood corpuscles treated with an appropriate 

 sensitizing substance from the rabbit are easily destroyed by nor- 

 mal dog serum. In a general way these facts have been known for 

 some time. Five years ago we mentioned an analogous series of 

 facts in showing that cholera vibrios treated with a little anti- 

 cholera sensitizing substance (that is to say, immune serum from 

 a goat heated to 55 degrees) were changed in vitro into roundish 

 granules when subjected to normal serum from the guinea-pig, 

 rabbit, rat, man or goat. More recently we added to this list sera 

 of the dog, hen and pigeon. $ In these instances the sensitized 

 vibrios are affected by the alexins present in normal sera. 



The same facts hold for corpuscles. 



For completeness we must recall an already published observa- 

 tion. A year ago we first mentioned that sensitized corpuscles 

 are not indiscriminately dissolved by any normal serum, or, in 

 other words, by every alexin. For example, sensitized hen cor- 

 puscles (hemolytic serum from the rabbit heated to 55 degrees) 

 are readily dissolved by several normal sera, but remain quite intact 

 in normal hen serum. This seems then to be a certain contradiction 

 to the statement that sensitized rabbit corpuscles are destroyed by 

 rabbit serum. When we mentioned this apparent contradiction a 



* If the energy of the sensitizing substance is slightly diminished, small doses 

 of rabbit serum will frequently fail to dissolve the corpuscles, although under the 

 same conditions normal guinea-pig serum is still very effective. 



t Munchener medicinische Wochenschrift, 1900. 



t See p. 180. 



See p. 173. 



