Formation of Antibodies. 



135 



the reaction for horse serum was somewhat longer, 18 to 39 days, 

 and the appearance of the precipitins slightly slower than in rab- 

 bits, since they were not obtained in human beings until the 6th 

 to the 15th day after injection. The injection of horse serum in 

 all these cases was followed by severe serum disease, lasting 

 from 11 to 28 days, and as a rule the precipitins appeared first 

 or their concentration increased markedly towards the end of the 

 serum disease. On the other hand, the reaction for horse serum 

 diminished rapidly towards the termination of the serum disease 

 and disappeared shortly thereafter. The intensity of the serum 

 disease and the persistence of the reactions for horse serum in the 

 circulation bore no direct relationship to the amount of serum 

 injected. 



In the second group were five cases to whom 300 to 500 c.c. 

 of horse serum were given. In this group the results differ 

 entirely from those obtained in rabbits and in the patients of the 

 first group. One characteristic of these cases is the persistence 

 in the blood of the reaction for horse serum over a very long 

 period of time which ranged from 49 to 67 days. Practically all 

 of these patients were lost to observation before negative reactions 

 for horse serum were obtained. Secondly, the precipitin formation 

 was either of extremely short duration or entirely absent. In 

 the third place, these patients either had very mild serum disease 

 lasting from one to five days or had none at all. 



There was one other case receiving 630 c.c. of serum who 

 showed the persistence of the reaction for horse serum in the 

 circulation for over 75 days; he also showed precipitins and he 

 had severe serum disease lasting 12 days. This is an exception 

 to the cases in both groups. 



An analysis of these observations shows that the reaction for 

 horse serum disappeared fairly promptly from the blood of indi- 

 viduals who had severe serum disease and who formed precipitins 

 towards horse serum, and that the disappearance of the antigens, 

 that is the horse serum, came shortly after the subsidence of the 

 serum disease, and when the precipitins were present in the largest 

 concentrations. On the other hand, in the second group the 

 reaction for horse serum persisted in the blood over long periods of 

 time. In these patients the precipitin reaction was absent or 

 slight and serum disease was absent or of very mild type. 



