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Scientific Proceedings (106). 



precipitin, anaphylactic antibodies, and skin hypersensitiveness 

 to horse serum appeared as a rule toward the termination of the 

 serum sickness. It was considered that the excessive production 

 of antibodies followed the cellular reaction which was made evident 

 by the serum sickness. In two of the cases that were studied, 

 serum disease did not follow the injection of horse serum and 

 anti-bodies did not appear in the circulation. The reason for this 

 variation in susceptibility, a condition that has long been puzzling, 

 has not been satisfactorily explained. 



The object of the present investigation was to determine, if 

 possible, whether the presence of antigen, namely, horse serum, 

 bore any relation to serum disease or to the production of anti- 

 bodies. It is known that by the method of specific precipitation 

 a reaction for horse serum may be obtained in the blood, both of 

 animals and of human beings, for many days after the injection 

 of horse serum. Since reactions for horse serum cannot be ob- 

 tained in the urine, it is improbable that horse serum is secreted 

 as such by the kidneys. 



The method employed has been to estimate by means of specific 

 precipitin reactions the presence of horse serum at given intervals 

 after its injection into human beings for therapeutic purposes in 

 pneumonia and at the same time to follow the appearance and 

 curves of precipitin for horse serum. Preliminary observations 

 on rabbits showed that when 5 c.c. of horse serum per kilo body 

 weight was injected intravenously, reactions for horse serum could 

 be obtained in the blood of the rabbit over a period of from 7 days 

 to three weeks. Precipitin for horse serum appeared in from 

 6 to 10 days and persisted for from 4 to 7 weeks. It is well known 

 that animals differ widely in their ability to form antibodies, 

 and observations on six rabbits showed considerable variation in 

 the rate of precipitin formation, and in the duration of the re- 

 action for horse serum in the circulation. 



By this same method we have studied 14 individuals who 

 have received from 100 to 500 c.c. of antipneumococcus horse 

 serum intravenously. An analysis of these cases shows that they 

 fall into two groups: In one group of eight cases the curve of 

 precipitin formation and the persistence of horse serum was 

 much the same as that observed in rabbits. The persistence of 



