HVPERSENSIT IVENESS TO HORSE SERUM. 



9 



scrutiny of the results obtained by the subcutaneous test seems to 

 show that the maximum of reaction is developed about the end of 

 the third or fourth week. The incubation period is thus not 

 sharply limited. The reaction is probably a slowly disappearing 

 one but it may persist for a very long time — twenty two months 

 in one of my cases. 



The hypersensitive mother guinea pig transmits her abnormal 

 condition to her offspring. In our experience about 50 per 

 cent, of such offspring reacted. Members of the same litter 

 tested with the same dose on the same day may either die very 

 quickly or show almost no reaction. The fact of transmission 

 from mother to offspring is strong presumptive evidence for the 

 view that the reaction depends on the development of a special 

 antibody by the sensitizing dose which is effective at the second 

 treatment. 



Such an antibody can be demonstrated by the passive transfer 

 of the blood or blood serum of hypersensitive guinea pigs to normal 

 guinea pigs. I have performed this experiment repeatedly. Thus, 

 choosing hypersensitive animals that have reached the full period 

 of reaction, I bled and injected 1 5 c.c. of defibrinated blood or 

 blood serum into the peritoneal cavity of a fresh guinea pig 

 weighing about 230 gms. After twenty four hours 1 or 2 c.c. of 

 normal horse serum injected intracardiac killed this animal, which 

 exhibited the typical symptoms. This fatal reaction at twenty four 

 hours I believe to be distinct from the reaction obtained by Gay 

 and Southard two weeks after the transfer of from o. I c.c. to 1 c.c. 

 of hypersensitive blood. This latter reaction is probably due, as 

 they supposed, to a retained horse-serum element or " rest " which 

 actively sensitizes the animal. The hypersensitive antibody is not 

 destroyed by heating to 60 0 C. for half an hour. Thus far further 

 study of its properties has not been made. 



If the hypersensitive animal is treated with a considerable, but 

 not fatal dose of horse serum it is for some time less or not at all 

 hypersensitive. This refractory or immune state can be very rap- 

 idly developed. The conditions are best illustrated by the fol- 

 lowing experiment. 



Three hypersensitive guinea pigs were bled. Mixed blood 

 was tested on a normal animal and found capable of transferring 



