MODE OF ACTION OF CYTOLYTIC SERA. 233 



sensitized cell with which it comes in contact. It would be well, 

 then, to give up the terms Zwischenkorper, Amboceptor, and Com- 

 plement, words chosen under the domination of theories which, 

 although ingenious, and capable of having advanced science 

 by the experiments they have suggested, are not justified by 

 experiment.* 



This experiment we have just quoted is similar to those we have 

 already discussed in previous articles. We wish here simply to 

 emphasize more fully the conclusions that may be drawn from 

 them; it also seems wise to repeat the experiment with certain 

 variations to show tnat it invariably gives the same results. 



For example, we can make a mixture of 0.5 of a cubic centi- 

 meter of fresh unheated, normal guinea-pig serum, 2.5 c.c. of 

 heated serum from a guinea-pig immunized against rabbit blood 

 and 2.5 c.c. of heated serum from a guinea-pig immunized against 

 hen blood. One-tenth of a cubic centimeter of this mixture, con- 

 taining alexin and the two sensitizers, destroys 0.1 of a cubic centi- 

 meter of defibrinated washed hen blood. The hen blood, however, 

 remains intact in twice the amount of mixture, 0.2 of a cubic 

 centimeter, if there has previously been added to it 0.3 of a cubic 

 centimeter of washed rabbit blood. The rabbit corpuscles are 

 destroyed and absorb all the alexin present without leaving any for 

 the hen-corpuscle sensitizer. 



In a similar mixture of fresh normal guinea-pig serum, heated 

 guinea-pig serum affecting rabbit blood, and heated rabbit serum 

 active against hen corpuscles, the reverse experiment may be per- 

 formed. This mixture is divided in equal parts. To one is added 

 corpuscles A and a few hours later corpuscles B ; to the other, first 

 B, then A. As in the preceding experiments, the introduction of 



* In the experiment just considered there is a third mixture C containing, as the 

 others, 0.2 of a cubic centimeter of fresh hemolytic serum specific for rabbit cor- 

 puscles. Instead of heated rabbit serum active against hen corpuscles it contains 

 the same amount (1 c.c.) of heated normal rabbit serum. When 0.6 of a cubic 

 centimeter of hen blood is added there is no hemolysis. On adding 2 drops of 

 rabbit blood hemolysis is as rapid as in B. Since B and C act alike we conclude 

 that neither the sensitizer for hen corpuscles, nor hen corpuscles themselves, are 

 able alone to absorb alexin; the two must be united to produce this result. As 

 we have already shown in a similar experiment (see p. 186), corpuscles from 

 species other than the one affected by the sensitizer that is present leave the 

 alexin unchanged. 



