262 Chapter IX 



animal body itself, but only under certain conditions when the 

 degree of immunity of the animal is sufficiently high and when 

 the bacilli introduced are not too numerous " (p. 130). In the case of 

 the typhoid bacillus, a certain degree of agglutination is produced 

 inside the animal body, but it is markedly increased in the fluids 

 that have been withdrawn and exposed to the action of the air. 



It has been demonstrated, repeatedly, that the agglutination of 

 micro-organisms by their specific serums does not prevent their 

 growth and multiplication. These agglutinated organisms lose none 

 of their virulence. Issaeff 1 , working in my laboratory, carried out 

 an investigation on this point in the case of the pneumococcus. 

 He vaccinated rabbits against this organism and satisfied himself 

 that the organism still grows well in the blood serum of such 

 rabbits; but, instead of presenting the typical form of lanceolate 

 diplococci, the pneumococcus, under these conditions, forms very 

 long chains of true streptococci. Having filtered the cultures in 

 order to get rid of the serum, he injected them into rabbits and 

 mice and demonstrated that the pneumococci had retained to the 

 full their initial virulence. Sanarelli 2 carried out corresponding 

 experiments with Gamaleia's vibrio, which, as we know, also forms 

 chains in the serum of vaccinated animals. When filtered on a paper 

 filter and washed with physiological saline solution, the vibrios were 

 found to be just as virulent as were the control vibrios grown in 

 [276] the serum of susceptible animals. More recently, Mesnil 3 demon- 

 strated the same point in connection with the bacillus of swine 

 erysipelas. He experimented on cultures that were agglutinated 

 after their formation and also on others agglutinated as they were 

 growing. The fluid of the culture was decanted and replaced by 

 fresh broth until the elimination of the serum was complete. Mice, 

 inoculated with the washed clumps, died in the normal period, thus 

 affording proof that "agglutination in no way alters the vitality 

 and virulence of the bacillus of swine erysipelas " (p. 492). 



We can readily understand, after the demonstration of these 

 various facts, that it is impossible to maintain Max Gruber's theory 

 that the agglutinative power constitutes the fundamental basis of 

 acquired immunity. Hence this writer, after publishing several pre- 

 liminary notes in 1896, has not yet decided to give to his hypothesis 



1 Ann. de VInst. Pasteur, Paris, 1893, t. vn, p. 260. 

 a Ann. de VInst. Pasteur, Paris, 1893, t. vn, p 225. 

 8 Ann. de VInst. Pasteur, Paris, 1898, t xn, p. 481. 



