6 COLLECTED STUDIES IN IMMUNITY. 



by the blood-cells, the clear fluid should be free from the same. To 

 prove this we have merely to add to some of this clear fluid sheep 

 blood-cells, and a sufficient amount of addiment in the form of normal 

 serum. If the fluid is free from immune body, the blood-cells will 

 remain undissolved. The centrifuged sediment must likewise be 

 tested for the presence of immune body. The sediment, freed as 

 much as possible from fluid, is mixed with salt solution and a suffi- 

 cient amount of addiment. If a corresponding amount of immune 

 body has been anchored by the blood-cells, they will now dissolve. 

 One of our numerous experiments follows:, 



4 cc. of a 5% mixture of sheep blood-cells are mixed with 1.0 

 or 1.3 cc. inactivated serum from our immunized goat. This is allowed 

 to stand for fifteen minutes at 40 C. and then carefully centrifuged. 

 The supernatant clear fluid is poured off, mixed with 0.2 cc. normal 

 sheeps blood and then with 0.8 cc. serum from a normal goat. This 

 mixture after being kept in a thermostat at 37 C. for two hours 

 and then allowed to settle in the cold, shows no trace of solution. 



The centrifuged sediment, freed as much as possible from fluid 

 by means of filter paper, is mixed with 4 cc. physiological salt solu- 

 tion and with 0.8 cc. normal goat serum. This mixture after being 

 kept for two hours in a thermostat at 37 C. is found completely 

 dissolved or very nearly so. 



In this experiment in which a sufficient amount of immune body 

 was used, we see that complete union took place between the immune 

 body and the blood-cells, resulting in the entire abstraction of the 

 former from the fluid. We have found that the same takes place 

 at lower temperatures, even at C. That this is a chemical union 

 and not a mere absorption is seen by experiments with other species 

 of blood. Thus the red blood-cells of rabbits and of goats have no 

 affinity whatever for this immune body. 



As a result of these experiments, therefore, and in conformity with 

 the side-chain theory, we must assume that the immune body possesses 

 a specific haptophore group which anchors it to the blood-cells of the 

 sheep. 



The next important question was that concerning the relation 

 of the addiment to the red blood-cell. This was studied in a manner 

 exactly similar to that of the previous experiment. Blood was 

 mixed with addiment, the mixture centrifuged, and the two por- 

 tions tested separately, by the addition of immune body, for the 

 presence of addiment. We varied our experiments greatly so far 



