292 STUDIES IN IMMUNITY. 



other. After contact the corpuscles are carefully washed, centrifu- 

 galized, and the supernatant fluids decanted; 1.5 c.c. of salt solu- 

 tion is then added to each tube. In one tube, then, the blood is 

 sensitized and in the other it is not. 



In the same way hen blood, sensitized and not sensitized, is 

 prepared by treating it with each specific serum. 



Antiserum is then diluted with an equal volume of normal guinea- 

 pig serum, 56 degrees, to facilitate mensuration. We refer to this 

 as diluted antiserum.* We then prepare the following mixtures 

 of antiserum and the two ox bloods treated as described: 



Tube A. Sensitized ox blood, 1 c.c.; diluted antiserum, 2.5 c.c. 



Tube B. Same as A, with non-sensitized ox blood in place of sensitized blood. 



One hour later the tubes are centrifugalized and the supernatant fluids A and 

 B decanted. Fluid A is deprived of antisensitizer, as may be imagined. These 

 fluids are used in making the following tubes: 



Tubes C and D. Each contains 1 c.c. of fluid A; to C is added 0.1 of a cubic 

 centimeter of sensitized ox blood. To D is added 0.1 of a cubic centimeter of 

 sensitized hen blood. 



Tubes E and F. The same as tubes C and D respectively, with fluid B replacing 

 fluid A. 



In addition there are controls containing each 1 c.c. of normal guinea-pig serum, 

 56 degrees, and 0.1 of a cubic centimeter of hen or ox blood sensitized and not 

 sensitized respectively. These control the tubes containing antiserum. 



Three-quarters of an hour later 0.2 of a cubic centimeter of alexin (fresh 

 guinea-pig serum) is added to tubes C, D, E, F, and to the controls. 



There is no hemolysis in tubes E and F containing liquid B, in 

 which the antiserum has not been deprived of its antisensitizing 

 power by sensitized corpuscles. There is, of course, no hemolysis 

 in the controls with non-sensitized corpuscles and without anti- 

 serum. In tubes C and D that contain fluid A, in which the 

 antisensitizer has been previously used up by the sensitized ox cor- 

 puscles, the hemolysis of both the ox and the hen corpuscles takes 

 place as rapidly as in the controls without antiserum. The same 

 antisensitizer, then, neutralizes the two sensitizers under con- 

 sideration, which differ markedly, as one is specifically suitable 

 for ox corpuscles and combines with them, whereas the other 

 does not. 



* It may be noted that four parts of this antiserum completely protect one 

 part of the sensitized blood used against the subsequent action of alexin. In 

 a control tube in which the antiserum is replaced by normal guinea-pig serum, 

 56 degrees, hemolysis is complete in 5 minutes. 



