224 STUDIES IN IMMUNITY. 



fixation of alexin is superfluous in the case of antiproteus serum. 

 The proteus bacillus we have used gives a granular degeneration 

 similar to the one shown by the cholera vibrio in cholera serum 

 when placed in contact with fresh normal serum. 



We know that the vibrio, too, is slightly affected by normal guinea- 

 pig serum. Proteus vulgaris gives a complete granular transfor- 

 mation with a sizable dose of normal serum, but a much smaller 

 amount suffices if a little fresh or heated antiproteus serum is 

 added. This, of course, demonstrates the presence of a sensitizer 

 in the immune serum. 



But we have also done the alexin fixation experiment with Proteus 

 vulgaris. The expected result was obtained: the organism in the 

 presence of normal guinea-pig serum absorbs little or no alexin, 

 but, when affected by the specific serum, takes it up. In the latter 

 instance, of course, sensitized corpuscles are not destroyed. 



In the experiments up to this point we have uniformly employed 

 sensitized rabbit corpuscles (i.e., those treated with specific serum 

 from the guinea-pig heated to 55 degrees) to prove the presence or 

 absence of free alexin in the fluid. In view of the conception of 

 the unity of the hemolytic and bacteriolytic alexin as proved a year 

 ago we might have used as an indicator either other corpuscles or 

 sensitized bacteria, such as cholera vibrios, to show the presence of 

 free alexin by a morphological change. Such an experiment we 

 have performed with B. proteus vulgaris as an indicator: 



A 24-hour agar culture of Proteus vulgaris was suspended in 

 6 c.c. of salt solution. An agar culture of the cholera vibrio was 

 treated in the same manner. Fresh normal guinea-pig serum, as 

 alexin, and heated proteus serum and cholera serum were also at 

 hand. The following mixtures were prepared: 



(a) Alexic serum, 0.2 c.c.; proteus emulsion, 0.3 c.c.; proteus 

 serum, 56 degrees, 0.6 c.c. 



(b) Alexic serum, 0.2 c.c.; proteus emulsion, 0.6 c.c.; normal 

 guinea-pig serum, 56 degrees, 0.6 c.c. 



(c) Same as "a," without bacteria. 



(d) Same as "b," without bacteria. 



Five hours later 0.2 of a cubic centimeter of the following mixtuiv 

 was added to each tube: Emulsion of cholera vibrios 0.5 cubic 

 centimeter, cholera serum, 1 cubic centimeter 56 degrees (from a 



