Contagious amd EpizooUo Diseases. 67 



was repeated some time later. The inoculations were made 

 at least twice, with intervals of one or several days. 



Tlie results in the case of the swine have been criticised 

 mainly, it would appear, because similar attempts on pigeons 

 proved unsatisfactory, tinless a greater number of inocula- 

 tions with the sterilized virus were resorted to. Such criticism 

 is, however, entirely unwarranted. 1st. Kesults obtained 

 in one genus of animals will not necessarily be secured in 

 another genus. 2d. No acquired immunity is absolute, not 

 even though it may have been secured at the expense of a 

 violent attack of the disease. In every case a large dose of 

 powerfully virulent material M'ill cause the best protected 

 system to succumb. All such protection is only relative, 

 and the fact that my inoculated pigs were unharmed by ex- 

 posure to infection and by inoculations with fresh virulent 

 liquids that proved fatal to other and unprotected pigs, 

 sufficiently attests that I was working on the right principle, 

 which even my critic and follower in the same line of exper- 

 iment has found satisfactory in his own hands. He need 

 not begrudge me the mead of priority in the work of estab- 

 lishing this great principle as applicable to swine-plague. 



Superiority of Prindple of Protection ly Sterilised 

 Virus. In comparing the method of protection by sterilized 

 virus witli the other inoculation methods, its great superiori- 

 ty becomes at once manifest. With the single exception of 

 Jenner's inoculation of a harmless disease (cow-pox) to protect 

 against a deadly disease (small-pox), all other inoculation 

 methods consist in the introduction into the animal system 

 of the living germs of the disease which it is sought to pro- 

 tect against. They are, one and all, but the production of a 

 mild form of the disease in question. Fundamentally, they 

 • are but a return to the pre-Jennerian principle of inoculating 

 from a mild case of small-pox, to protect against a deadly 

 form of the same disease. They all result in the multipli- 

 cation of these weakened gerj*is by myriads in the animal 



