260 Chapter IX 



In the serum of rabbits vaccinated against the Gentilly cocco- 

 bacillus, no filaments corresponding to those met with in the agglu- 

 tinative reaction are formed, but bacilli are produced. In spite of 

 this the animals that furnish the serum show a distinct resistance 

 to infection. More recently, Karlinski^ has studied the properties of 

 the serums of animals treated with the cocco-bacilli of hog cholera 

 and swine plague. He was able to demonstrate that blood serum 

 from oxen that had received repeated injections of cultures or toxin 

 of hog cholera, was not only incapable of killing the cocco-bacilli of 

 the two swine diseases but it even "gave rise to no agglutination " of 

 the two bacilli and did not arrest the motions of those of hog cholera. 

 On the other hand, serums have been obtained from other species 

 of animals (dog, pig) which brought about the typical agglutination 

 of the cocco-baciUus of hog cholera^. 



In tlie preceding chapter, Gengou's experiment on the serum of 

 a dog that had been treated with a virulent culture of anthrax has 

 already been cited. This serum did not agglutinate the bacillus, 

 even of the first vaccine of Pasteur. Nevertheless, a second dog 

 treated with an attenuated culture of this bacillus furnished an 

 agglutinative serum. The immunisation of the first dog was carried 

 very much further than that of the second, but the agglutinative 

 properties were in inverse order. Sawtchenko, in his study of im- 

 munity against anthrax, demonstrated that the subcutaneous exu- 

 ['^V4] dation from vaccinated rats does not agglutinate the bacillus which 

 usually exhibits such a great tendency to collect into clumps. 



Agglutination has been studied particularly carefully in typhoid 

 fever. We know that after an attack of this disease, an acquired 

 refractory condition is produced which lasts for a considerable period. 

 In most cases the agglutinative power of the blood diminishes very 

 rapidly, and disappears a few weeks after the commencement of 

 convalescence. It is only in rare cases that it persists for years ^. 

 On the other hand, during tlie period of apyrexia which precedes 

 the relapse in typhoid fever and during the period of relapse, 

 the agglutinative power may manifest itself in a very marked 

 degree. In an observation made on a case reported by Widal and 



1 Ztschr.f. Hyg., Leipzig, 1898, Bd. xxvm, S. 406. 



2 Fifteenth Ann. Rep. of the Bureau of Animal Industry for 1898, Washington, 

 1899, p. .348, PI. XI. 



^ Widal et Sicard, Bull, et Mem. Soc. med. d, hop.y Paris, 1896, p. 684 [Semaine 

 med., Paris, 1896, p. 514], 



