Mechanism of immunity against micro-organisms 191 



does not circulate in the blood plasma nor in that of the exudations, 

 and this is a sufficient reason for refusing to it the title of a secretion- 

 product. Its presence in the blood serum is due, like that of the 

 fibrin-ferment, to the destruction or more or less grave injury of 

 the phagocytes. 



This fact, upon which we must insist most strongly, is in flat con- 

 tradiction to the view recently formulated by Wassermann 1 . In a work 

 devoted to natural immunity against micro-organisms, this author 

 describes how he submits his animals (guinea-pigs) to the action of an 

 anticytase (or anti-alexine) serum whose preparation, described in the 

 fifth chapter of this work, offers no difficulties. Under the influence of 

 this serum, the guinea-pigs, into the peritoneal cavity of which a strong 

 dose of typhoid cocco-bacilli is inoculated, die from infection, whilst the 

 control animals, inoculated in a similar manner, but which have re- 

 ceived in addition some normal rabbit's serum, heated to 60 C., entirely 

 resist the infection. Wassermann concludes that the first series of 

 guinea-pigs succumbed because of the impossibility of fighting against 

 the typhoid bacillus by means of the free cytase, this being neutralised 

 by the anticytase serum. The fact pointed out by Wassermann is 

 perfectly accurately stated and has been confirmed by Besredka 2 , in 

 an investigation carried out in my laboratory. Nevertheless, it is 

 impossible to accept Wassermann's view as to the part played by [202] 

 anticytase in his experiment. As clearly demonstrated by Besredka, 

 the anticytase serum acts not merely by neutralising the bactericidal 

 ferment, but also by its other properties, especially by one which 

 prevents the stimulation of the phagocytes. 



In the struggle of the guinea-pig's organism against a strong 

 dose of typhoid cocco-bacilli (in Wassermann's experiments 40 times 

 the lethal dose), the free cytase plays a part so infinitely small that 

 even the injection into a guinea-pig of a large quantity of serum (3 c.c.) 

 from a normal guinea-pig (containing much cytase) does not prevent 

 the death of the animal. It is only the blood serum of other species 

 (rabbit or ox) that is capable of protecting a guinea-pig against such 

 a large quantity of typhoid bacilli. 



Wassermann was in error in supposing that his experiment was a 

 case of natural immunity. It comes entirely within the range of the 

 phenomena of acquired immunity. In fact, the natural immunity 

 of the guinea-pig is only exhibited against a dose 40 times less than 



1 Deutsche med. Wchmchr., Leipzig, 1901, S. 4. 



2 Ann. de VInst. Pasteur, Paris, 1901, t. xv, p. 209. 



