Mechanism of immunity against micro-organisms 195 



has shown that the whole of the cytase has not been absorbed by 

 the red corpuscles, we readily understand that the portion re- 

 maining in the fluid will act on the normal red corpuscles of another 

 ^species. 



But when we fix the cytase to the sensibilised red corpuscles the 

 ibsorption becomes complete and the addition of other species of 

 }d corpuscles no longer produces any solution. It is easy, therefore, 

 )y means of sensibilised red corpuscles, to take out the whole of the 

 jytase from a serum. When to such a serum, thus deprived of the 

 rhole of its haemolytic cytase, we add bacteria, these latter show no 

 sign of disintegration ; whilst previously, that is before the absorption 

 )f the cytase by the sensibilised red corpuscles, the same serum was 

 lighly bactericidal. Let us take a concrete example so that the reader 

 may form some definite idea of the phenomena observed. Take a 

 normal rat's serum which, in a very short time, transforms cholera 

 vibrios into granules or deforms and dissolves anthrax bacilli. The 

 same serum dissolves the red corpuscles of a difierent species. We 

 will first leave this serum in contact with these red corpuscles sensi- 

 bilised by the specific fixative. After the solution of a quantity of 

 these red corpuscles, let us add to the serum a few cholera vibrios 

 or anthrax bacilli. The vibrios, in this serum, are no longer trans- 

 formed into granules and the anthrax bacilli undergo no change at 

 all ; they stain in the normal fashion by basic aniline dyes, they [206] 

 present neither deformations nor solution of their contents. In 

 other words, no bactericidal action takes place in a serum that is 

 deprived of its cytase by sensibilised red corpuscles. 



Is it necessary to conclude from this and other analogous experi- 

 ments that the cytase, fixed by the sensibilised formed elements (red 

 blood corpuscles or micro-organisms), is always one and the same 

 cytase ? INIay it not be that these elements, impregnated with specific 

 fixatives, become so greedy for cytases that it is easy for them to 

 absorb not only one variety but several species of cytases ? 



The facts we have summarised in Chapter lY concerning the 

 cytases, indicate that very probably there exist two kinds of cytases, 

 connected with the two great groups of phagocytes. Extracts of 

 the mesenteric glands, of the omentum and of the exudations, which 

 are composed for the most part of microphages, do not dissolve the 

 red corpuscles, but are, on the other hand, specially bactericidal. 

 Sarassewitch has carried out numerous experiments on this point 

 in my laboratory and has brought forward a large number of data 



13—2 



