320 Chapter X 



by these serums. It may be useful, therefore, to pass in review the 

 protective action of fluids less complicated than blood serums. 



Issaeff; in the work already cited, demonstrated that not only 

 normal serums but a whole series of fluids, such as urine, broth, etc., 

 exert a protective effect against microbial infections. These fluids 

 must be injected about 24 hours before the introduction of the 

 bacteria. The best method consists in injecting them directly into 

 [336] the peritoneal cavity, after which the animals acquire an immunity 

 against absolutely fatal doses of cholera vibrios. Funck verified this 

 observation for the infection caused by the typhoid cocco-bacillus, 

 and Bordet confirmed it for the streptococcus. The injection of 

 peptonised broth into the peritoneal cavity of the normal guinea-pig, 

 made 24 hours before an inoculation of double the fatal dose of the 

 streptococcus, exerts a distinct protective action ; the infection does not 

 kill the animal. This broth is neither bactericidal, attenuating, nor 

 agglutinative ; it forms a good culture medium for the streptococcus 

 and possesses no fixative power. Consequently it does not act directly 

 on the vitality or virulence of the micro-organism ; nevertheless, it is 

 distinctly protective. 



According to Issaeff's researches, the protective substances used 

 by him must be arranged in the following order as regards their 

 action against the cholera vibrio. Tuberculin is the most effective ; 

 then comes a 2% solution of nuclein, followed by normal human 

 serum, broth, and urine, whilst physiological saline solution is the 

 least active. All prevent infection by the vibrios, but the protection 

 is effective for some days only; this protective action is exerted 

 against various kinds of bacteria, being in no sense specific. 



Pfeiffer lays so much stress on the great difference between the 

 protective power of normal serums, as well as of the other fluids 

 mentioned, and that of the anti-infective specific serums, that he even 

 proposes to classify the first group as giving rise to pseudo-immunity 

 or resistance. This view is certainly an exaggerated one, because it 

 is difficult to draw a very distinct line between the two groups of 

 phenomena. There are normal serums, of which 0*1 c.c. is quite 

 sufficient to confer the protective effect, just as there are specific 

 serums of which it is necessary to make use of a much greater dose 

 to attain the same result. 



Protective fluids, other than the serums, only manifest their in- 

 fluence by exciting a great phagocytic "superactivity." As the result 

 of their injection into the peritoneal cavity of normal guinea-pigs, 



