Acquired immunity against micro-organisms 255 



cyaneus but also against several other bacteria, e.g. the bacilli of 

 anthrax, diphtheria, typhoid, and plague. This substance rapidly 

 breaks up these bacteria, and cures diphtheria and experimental 

 anthrax. But it is, at the same time, so affected by the invasion 

 of the most common bacteria, such as Bacillus subtilis, that it is 

 necessary to add antiseptics in order to preserve it. To these con- 

 tradictions, inaccuracies, and uncertainties must be added further 

 the advice, given by Emmerich and Low to bacteriologists, not to 

 attempt to reproduce their experiments, because they may easily 

 fail, and I think that, in spite of the seductiveness of the attempt 

 to attribute to bacterial products a share in the elaboration of anti- 

 microbial substances, we must conclude not to follow these authors 

 further. It is better to confess our ignorance of the chemical 

 composition of these substances in general and of the fixatives in 

 particular. 



As the fixatives resist temperatures much higher than those which 

 destroy the cytases, in this respect resembling the agglutinative sub- 

 stances so frequently found in the fluids of vaccinated animals, there 

 has long been a tendency to identify them with these latter. It is in- 

 disputable that between the fixatives and the agglutinative substances 

 the analogies are fairly numerous. Both are produced in quantity 

 during the process of immunisation, and are found not only in the 

 blood serum but also in the fluids of the living animal, especially 

 in the fluids of exudations and trausudations. Both dialyse through 

 parchment more readily than do the cytases. Buchuer 1 has demon- 

 strated that his alexines (bactericidal substances of normal serum) 

 will dialyse only where the lower fluid is pure water ; dialysis is nil 

 when the distilled water is replaced by physiological saline solution. 

 The fixatives and agglutinins, as demonstrated by Gengou 2 for the [269] 

 latter, pass almost completely through the dialyser in the case of pure 

 water, and one-half still passes when the lower fluid approaches as 

 nearly as possible to normal serum. 



In spite of these analogies, however, the agglutinative property 

 must be sharply distinguished from the fixative power of serums. In 

 this fluid, derived from normal animals, the agglutinative property is 

 often very marked when the power of fixing the cytases is totally, or 

 in great part absent. Bordet and Gengou 3 have demonstrated also 



1 Miinchen. med. Wchnschr., 1892, SS. 119, 982. 



2 Ann. de Flnsi. Pasteur, Paris, 1899, t. xnr, p. 647. 



3 Ann. de FInst. Pasteur, Paris, 1901, t. xv, p. 289. 



