276 Chapter IX 



and are only manifested after a long period of vaccination. Such is 

 the case with anthrax. After the discovery of protective serums, 

 numerous attempts were made to obtain a serum protective against 

 the anthrax bacillus. Several observers failed in their attempts, 

 others were more fortunate. Sclavo^ and Marchoux^ were the first 

 to succeed in obtaining a protective serum from animals hyper- 

 immunised against anthrax. They were able to show that the 

 serum of sheep, treated first with vaccines and then repeatedly 

 with anthrax virus, would protect rabbits against a fatal dose 

 [290] of the bacillus. Marchoux even obtained, with hyperimmunised 

 rabbits, a serum which prevented normal rabbits from contract- 

 ing fatal anthrax. Sobernheim^ was less fortunate in his first 

 experiments. He satisfied himself that the blood serum of cattle 

 that had recovered spontaneously from anthrax or that had been 

 vaccinated according to Pasteur's method, was absolutely unable to 

 protect small animals against the anthrax bacillus, and his hyper- 

 vaccinated rabbits furnished serums of doubtful activity. It was 

 only later that he succeeded* in obtaining better results ; especially 

 when he used sheep. Even then he found that in the production 

 of the anti-infective property the individuality of the immunised 

 animals had a dominant influence. Thus, in two sheep, treated in 

 exactly the same way, the serum of one was found to be incapable of 

 protecting a rabbit, whilst that of the other exhibited an undoubted, 

 although feeble, protective power. 



But what is of greater interest to us, from our point of view, is 

 that guinea-pigs which have been vaccinated against anthrax and 

 which enjoy a considerable immunity against this disease, exhibit no 

 protective power. In a letter from Behring I learnt that this fact 

 had for the first time been demonstrated by Wernicke in experiments 

 carried out in the Hygienic Institute at Marburg. After repeated 

 and painstaking attempts this observer succeeded in vaccinating 

 guinea-pigs against enormous doses of virulent anthrax bacilli. The 

 serum from the animals so immunised was, however, quite incapable 

 of protecting normal guinea-pigs against a fatal infection. This result 

 was the more extraordinary since Wernicke's pigeons, likewise vac- 



1 [Centralhl. f. Bakteriol, u. Parasitenk., Jena, 1895, Bd. xviii, S. 744]; Riv, 

 dllg. e San. Piibbl, Torino, 1896, t. vii, nos. 18—19 ; ihid. 1901, t. xii, p. 212. 



2 Ann. de VInst. Pasteur., Paris, 1895, t. ix, p. 785. 



3 Ztschr.f. Hyg., Leipzig, 1897, Bd. xxv, S. 301. 

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



