242 Chapter VIII 



power of the blood of vaccinated and normal sheep, he observed that, 

 in both cases, there was, at first, a certain decrease in the number of 

 bacilli sown, more marked in the blood of the vaccinated than in 

 that of the control animals. Nevertheless, 8 hours after the com- 

 mencement of the experiment the anthrax bacteria had produced 

 innumerable bacilli in the blood of the refractory sheep. Nuttall 

 satisfied himself that this feeble bactericidal power was not to be 

 compared with the very much greater power of the blood of the 

 rabbit, an animal specially susceptible to anthrax. 



More recently the properties of the serum of sheep which have 

 been vaccinated against anthrax have been studied very carefully by 

 Sobernheim^ He also was able to show that this serum allows of an 

 abundant development of the bacillus, and that, outside the animal, 

 it does not exercise any more appreciable bactericidal power than 

 does the serum of the normal sheep. The serum of the best vacci- 

 nated sheep was found to be incapable of destroying even very small 

 quantities of anthrax bacilli. The only change that Sobernheim could 

 make out was with regard to the thickening of the bacterial 

 membrane. This modification, however, was not constant and could 

 not be seen in the serum of certain vaccinated sheep. 



The serum of the sheep vaccinated by Sobernheim exhibited no 

 [255] increase of agglutinative power as regards virulent bacilli. Gengou^, 

 however, made it clear that repeated injections of cultures of the 

 first vaccine of Pasteur into dogs produced a marked augmentation 

 of this agglutinative power ; but it was only produced when the 

 attenuated bacillus was used. The virulent anthrax bacillus, de- 

 veloped as isolated rods, was not afiected in the least by serum 

 that was highly agglutinative for the bacillus of the first vaccine. 

 Gengou also made the converse experiment with the serum of a 

 dog into which he had previously injected a number of virulent 

 anthrax bacilli. The dog, naturally refractory to anthrax, resisted 

 the inoculation perfectly, but its serum did not acquire any 

 agglutinative power against the first vaccine. He concluded 

 therefrom that "the part played by agglutinins in the defence of 

 the animal must be regarded as extremely problem atical" (p. 339). 

 On the other hand the phagocytic reaction in the vaccinated sheep 

 is always very pronounced and constant. Von Behring^, in one of his 



» Ztschr.f. Hyg., Leipzig, 1899, Bd. xxxi, S. 89. 



2 Arch, internat. de Pharmacodyn., Gand et Paris, 1899, Vol. vi, pp. 303, 338. 



3 " Infectionsschutz und Immunitat" in Eulenburg's " Rcal-Encyclopadie d. ges. 

 Heilkimde," iii^^ Aufl. {Encyclop. Jahrhiicher), Wien, 1900, Bd. ix, S. 202. 



