406 STUDIES IN IMMUNITY. 



hemolytic alexin. The numerous and varied applications of this 

 method invariably show that the corpuscles used as an indicator of 

 alexin fixation remain intact, whatever be the sensitized cells em- 

 ployed in the first phase of the experiment, provided the sensitizer em- 

 ployed is sufficiently strong and the precautions mentioned are taken 

 in regard to the volume of salt solution. In a corresponding manner 

 account should be taken of the respective potency of the two sen- 

 sitizers which are successively used, in respect to the fixation of a 

 given alexin. If the first is not very powerful and does not remove 

 the last traces of alexin, the met hod may give very varying results, de- 

 pend ing on whether the corpuscles used as an indicator are moderately 

 or strongly sensitized, for the traces of alexin may be sufficient to 

 produce hemolysis in the latter case, whereas in the former instance, 

 owing to an antagonistic effect of the serum which tends to dis- 

 seminate the alexin, they may not. Two opposing forces of vari- 

 able energy tend to take hold of the alexin and the result depends 

 on the equilibrium established between them. With this idea in 

 mind it is easy to show that, following contact with a large 

 number of moderately sensitized corpuscles, a fluid containing 

 alexin may subsequently act on similar corpuscles as if no active 

 substance were present, but, on more highly sensitized corpuscles of 

 the same species, as if still present. It will scarcely be claimed that 

 the alexin used up by a feeble sensitization differs from the one taken 

 by a greater sensitization. Such, however, is apparently the con- 

 clusion of Remy.* This investigator mixes sensitized typhoid 

 bacilli with his alexin and finds that subsequently added cor- 

 puscles remain intact when sensitized by a serum of moderate 

 activity, whereas they are destroyed if the serum with which they 

 have been treated is very powerful; from this he concludes that 

 the bacteriolytic alexin differs from the hemolytic alexin. He 

 might equally well have concluded that there is an alexin partic- 

 ularly adapted for heavily sensitized corpuscles, since such cor- 

 puscles are hemolyzed in a fluid in which the same corpuscles, 

 more weakly sensitized, remain intact. In fact, Remy has usnl a 

 hemolytic serum that has a higher sensitizing power than his anti- 

 typhoid serum. 



* Contribution & l'e"tude des substances actives du seYum. Bull, de I'Academie 

 de Mddecine de Belgique, 1903. 



