396 STUDIES IN IMMUNITY. 



Metchnikoff * himself has accepted this view and ascribed to the 

 fixateur in general an adjuvant role in phagocytosis. Later, after 

 Wright's investigations had turned the discussion to the opsonin, 

 there were endeavors made to demonstrate opsonins for blood 

 corpuscles in specific hemolytic sera. Let us see if this was justi- 

 fiable. In experiments with an exudate of macrophages from a 

 rabbit I found that the washed leucocytes took up very actively 

 bovine blood corpuscles which had first been treated with specific 

 hemolytic sensitizer (inactivated rabbit > bovine serum) and 

 then with alexin (fresh horse serum) , but that only sensitized, not 

 alexinized, blood corpuscles were taken up by the leucocytes in 

 less degree. Washed untreated blood corpuscles were not taken 

 up by phagocytes. I repeated these observations with thrice- 

 washed dog leucocytes in the following manner: 



1. Leucocytes. 



Washed bovine corpuscles. 



2. Leucocytes. 



Sensitized bovine corpuscles. 



3. Leucocytes. 



Sensitized and alexinized bovine corpuscles. 



4. Leucocytes. 



Bovine corpuscles plus alexin. 



Contact, 1 hour at 37 degrees. The blood of 2 and 3 was washed 

 after each preparatory treatment with salt solution, whereby only 

 those constituents of the serum which the corpuscles had fixed 

 could develop any action, and all else was removed. The experi- 

 ment gave the result that in 1 and 4 the phagocytosis is about nul. 

 In 2 it is fairly strong, whereas in 3 there is hardly a macro- or 

 microphage which does not contain one or more blood corpuscles. 

 The free alexin (4) is not able, therefore, alone to stimulate phago- 

 cytosis, whereas it is able when the specific sensitizers are fixed to 

 blood corpuscles to increase (3) their already well-marked action (2). 



Similar experiments with another hemolytic serum (rabbit > 

 goat and goat corpuscles) gave entirely corresponding results. 



I have not yet observed a specific serum which was hemolytic 

 but not hemotropic, as reported by Neufeld and Topfer.f Our 

 results, however, show a distinct similarity with the findings of 



* Han<ll). d-r Pathog., Microorg., Bd. IV, Teil. I. 

 t Cent, fiir Bakt., Bd. XXXVIII, p. 456. 



