IOI 



prompted experimentation in regard to other diseases. In- 

 oculation of cattle with material from animals dead of in- 

 fectious pleuro-pneumonia lung plague was begun in 

 Holland in 1852, and soon extended to Germany and Rus- 

 sia. In Saxony the mortality, previously twenty-five to 

 thirty per cent, of the herds, became ten, six, two, even one 

 per cent. At the Cape of Good Hope, where seventy to 

 eighty per cent, of the cattle died of this infection, the 

 disease almost vanished after inoculation was extensively 

 practised. The tag- sore of sheep was always robbed of 

 many victims by artificial inoculation. But of the diseases 

 of whose parasitic origin we have conclusive or strong pre- 

 sumptive evidence, every one may occur more than once 

 in the same subject. It is evident therefore, first, that im- 

 munity against an infectious disease, in the ordinary 

 sense of the term, implies not necessarily the absence, 

 but merely a relatively slight degree of susceptibility ; 

 second, that the question must be studied as to each dis- 

 ease independently of all others. 



Although the question of protective vaccination has 

 been experimentally studied as to anthrax, charbon symp- 

 tomatique, chicken cholera, septicaemia, by Chauveau, 

 Toussaint, Semmer, Colin, and Rosenberger, yet the re- 

 sults are so closely associated with Pasteur's name and 

 with anthrax that I shall omit extended reference to the 

 pioneer workers and works, and consider as the most 

 favorable example, the well-known experimentation in 

 protecting sheep against anthrax by inoculation with the 

 cultivated bacilli. This method of Pasteur, I might say, 

 is the first one which has afforded results at all satis- 

 factory ; and the principle differs from that employed in 

 lung-plague, tag-sore, etc., in that the artificially cultivated 

 organisms isolated from the accompanying animal tis- 

 sues are employed a new departure therefore. 



In considering this subject, with which Koch's name 

 is almost as closely associated as Pasteur's, it is advisable 

 again to remember that this is a question of facts and 

 not of individuals ; that to us Gaul and Teuton are alike 

 friends, as we fortunately keep no watch on the Rhine ; 



