ALEXIN ABSORPTION. 405 



experimental method employed to demonstrate alexin fixation 

 consists, as we know, of two phases: In the first phase the alexin 

 is placed in contact with such cells as bacteria plus a serum "A" 

 that is capable (or supposedly capable) of sensitizing these cells, 

 that is to say, of conferring on them the property of fixing alexin. 

 In the second phase one determines, by adding sensitized blood 

 corpuscles, whether the alexin has disappeared from the fluid or 

 remained free in it ; in the latter instance the fixation takes place, not 

 during the first phase (on the bacteria) , but during the second phase 

 (on the corpuscles). As a result, hemolysis occurs, and the conclu- 

 sion is that serum "A" is not sensitizing, or, at best, only slightly so. 

 But it is evident that, for experimental accuracy, the two phases of 

 the experiment should be comparable in respect to the facility for 

 alexin absorption. As we have seen, an excess of serum inhibits 

 fixation and an excess of salt solution favors it; the effort, then, 

 should be to maintain a constant proportion between salt solution 

 and serum during the entire experiment. The sensitized corpuscles 

 finally introduced are suspended in salt solution; it is evidently 

 better to add the number of corpuscles desired, not by employing 

 a large volume (lc.c.,for example) of a weak suspension of corpuscles, 

 but a small volume of a thick suspension (0.1 c.c, for example). 

 If, for example, the first mixture is: alexin, 0.1 c.c, plus bacterial 

 suspension 0.3 c.c, and 0.3 or 0.5 c.c of the serum in which the pres- 

 ence of abacterial sensitizer is to be determined, the fixation of alexin 

 on the bacteria will be opposed by the large proportion of serum 

 in the mixture and may be complete only in case the sensitizer is 

 very strong. If much salt solution is added with the red blood 

 corpuscles, the antagonistic effect is removed and a most minute 

 trace of free alexin will produce hemolysis. And as the antimicrobial 

 sensitizer has been handicapped by the hemolytic sensitizer it may 

 easily escape detection. Or, indeed (and this error would seem to us 

 to have been committed),* one might conclude that the alexin fixed 

 by a given cell (bacterium, for instance) is not identical with the one 

 fixed by a different cell (corpuscle), and might be led to agree with 

 the erroneous hypothesis that the bacteriolytic alexindiffers fromthe 



* We think that certain experiments of Moreschi that seem to indicate a 

 plurality of alexins are open to criticism from this standpoint. (Berlin klin. 

 Wochen., 1907, 1206); this investigator usually employs a large volume of salt 

 solution in which to suspend his sensitized corpuscles (1 c.c). 



