AGGLUTINATION AND DISSOLUTION. 181 



heated to 55 degrees; and at the same time are deprived of their 

 activity against corpuscles. The differences in alexins from dif- 

 ferent sources, so far as their action on corpuscles is concerned, are 

 not to be reckoned with when dealing with vibrios. 



Although the presence of alexins is not distinctive of the sera of 

 vaccinated animals, since they occur in the same form in normal 

 serum, the agglutinating properties of the serum of vaccinated 

 animals are clearly to be distinguished from those of normal sera as 

 more intense and specific. It is worth considering, however, whether 

 the agglutinins in immunized animals, in spite of these differences, 

 are affected in the same way by heat as are the agglutinins of 

 normal sera. 



We may begin by establishing to what extent heat weakens the 

 agglutinating power of a given normal serum for corpuscles and 

 for bacteria respectively. For such an experiment bacilli easily 

 clumped by various normal sera are chosen. We have particularly 

 employed the bacillus typhosus. Without going into the details 

 of these experiments we may say in general that a given high tem- 

 perature causes a normal serum to lose its property of agglutinating 

 both bacteria and cells to an equal extent. In the sera that we 

 have tried the agglutinating properties remain unaffected after 

 heating to 55 degrees for half an hour. Heating to 61 to 62 degrees 

 for the same period diminishes but does not entirely destroy the 

 agglutinating properties of guinea-pig, goat, dog, horse and hen 

 serum. With poorly agglutinating sera there is practically no 

 clumping action after heating to this degree: when dealing with 

 strongly agglutinating sera it is still very distinct after such treat- 

 ment. Hen serum, for example, even after heating to 67 degrees 

 still agglutinates rabbit corpuscles distinctly. As the temperature 

 is raised the agglutinating power becomes weaker and weaker, so 

 that normal sera heated for a half hour to 70 degrees no longer 

 agglutinate. 



are, however, in certain sera bactericidal substances quite distinct from alexins. 

 Rat serum heated to 55 degrees is quite incapable of producing a transformation 

 in cholera vibrios, sensitized with cholera serum, although this property is present 

 in intact rat serum. But such heated rat serum destroys the anthrax bacillus 

 with apparently undiminished activity. Sawtchenko has already noted that this 

 particular bactericidal property of rat serum for the anthrax bacillus resists 

 heating to from 55 to 60 degrees. 



