12 COLLECTED STUDIES IN IMMUNITY. 



and Feb. 24) of two male goats by injecting them subcutaneously 

 with increasing amounts of defibrinated sheep blood. In a short 

 time a strongly active serum was produced in both animals, and 

 we were able to observe how, following the general laws of immu- 

 nization, its activity increased. The course of the immunization 

 did not manifest any peculiarities. It should, however, be remarked 

 that on the days following the injection of a considerable amount 

 of blood (350 cc.) not the least decrease in the activity of the serum 

 could be observed, in contrast to the experiences with tetanus or 

 diphtheria immunization. 



So far as the general method employed in the following experi- 

 ments is concerned, it was the same as that mentioned in the first 

 paper. The blood was always used in the form of a 5% suspension 

 in physiological salt solution. At the time of these experiments 

 the serum of buck I was able to dissolve the sheep blood com- 

 pletely in the proportion of 0.2-0.3 cc. serum to 5 cc. sheep blood 

 mixture; 0.03-0.07 cc. serum w r ere able to produce a just noticeable 

 amount of solution. Of the serum of buck II, 0.15-0.2 cc. suf- 

 ficed for complete solution. It should be mentioned that the serum 

 of buck II even before immunization possessed a slight solvent 

 effect on sheep blood. This, however, was so slight that 4.0 cc. of 

 the serum were not nearly able to dissolve 5 cc. of the 5% blood 

 mixture, and 1.2 cc. serum produced only a just noticeable amount 

 of solution. Heating the serum to 57 C. for half an hour destroyed 

 this action, as it did also that for rabbit and guinea-pig blood. 1 



With the sera of these two bucks we were now able to proceed 

 with our experiments. The combination of the immune body with 

 the erythrocytes of the sheep at C. can be readily demonstrated, 

 for at this temperature and by the employment of proper amounts 

 of serum no solution takes place. The serum was allowed to act on 

 the sheep blood for twenty-four hours, care being taken to keep the 

 mixture at C. The blood-cells were then separated by means 



1 On examining the sera of a large number of normal goats one will find 

 some sera which possess this feeble solvent power for sheep blood. Thus the 

 normal goat sera which we employed for control tests in our first experiments, 

 and which were used in great number, failed absolutely to show any solvent 

 action, but at most manifested only a variable degree of agglutinating action. 

 This will be seen from our reports at that time. In our first communication 

 we had already called attention to the great variability of the agglutinating 

 property. 



