AGGLUTINATION AND DISSOLUTION. 171 



The specificity of rabbit serum active against hen blood. — We have 

 not done many experiments on this subject, but it seems certain 

 that this serum is quite as specific from all appearances as are 

 antimicrobial sera. This active rabbit serum naturally enough has 

 no effect on rabbit corpuscles and it also has no more effect on 

 guinea-pig corpuscles than has normal rabbit serum; nor does it 

 have a distinctive action on pigeon, human or mouse corpuscles. 

 With none of these corpuscles is the agglutination and energetic 

 dissolution that occurs with hen corpuscles to be noted. 



The fixation by corpuscles of the specific substances of antihematic 

 serum. — Corpuscles that are susceptible to a given antihematic 

 serum fix the active substances of this serum. We have already 

 considered this fact in a recent article;* and have also noted that 

 bacteria absorb all the active substances from antimicrobial sera in a 

 similar manner. Corpuscles that are not affected by a serum do not 

 absorb its active properties and this remark applies to normal sera 

 as well as to specific sera. For example, if normal hen serum is 

 added to rabbit corpuscles the corpuscles are energetically agglu- 

 tinated ; and the supernatant fluid is found to be deprived of agglu- 

 tinating properties for fresh rabbit corpuscles. But if hen serum 

 is placed in contact with corpuscles that it affects only slightly, for 

 example, with guinea-pig corpuscles, the supernatant fluid still 

 retains its agglutinating property for susceptible corpuscles. 



The technique employed in absorbing the active principles of an 

 antihematic serum follows : the active serum employed is heated to 

 55 degrees for half an hour and thereby deprived of its dissolv- 

 ing effect. The following mixtures are then made in test tubes: 



A, 3 c.c. of normal rabbit serum plus 0.5 of a cubic centimeter of active guinea- 

 pig serum. 



B, 3 c.c. of defibrinated rabbit blood plus 0.5 of a cubic centimeter of active 

 guinea-pig serum. 



The first tube is a control. Both tubes contain equal amounts of active serum 

 diluted in a similar manner. The second tube, however, contains corpuscles, 

 whereas the first does not. After contact the tubes are centrifugalized and the 

 supernatant fluids decanted. The clear fluids thus obtained are tested for agglu- 

 tinating property. Fluid A, which has not been subjected to corpuscles, aggluti- 

 nates rabbit corpuscles energetically whereas fluid B does not agglutinate them. 

 A determination is then made of the power of the two fluids to form hemolyzing 

 mixtures with alexin, as follows: 



* Mechanism of agglutination, p. 142. 



