46 



the cultivation is carried on, the successive pro- 

 ducts of descent may be gradually weakened until 

 they become harmless. Such being the case, any 

 desired degree of attenuation may be obtained, and 

 by inoculation with a virus brought down to the 

 proper strength the non-fatal afifection may be 

 occasioned which gives immunity from subsequent 

 liability to take the disease under exposure to 

 contagion. The knowledge thus acquired has been 

 already practically turned to account upon a large 

 scale for checking the ravages of that exceedingly 

 fatal disease amongst cattle known as anthrax, 

 or splenic fever, and through the success attained 

 much sacrifice of life has been averted. 



If this can be accomplished for one disease, and 

 more than one can be mentioned, is there not 

 ground for believing that means will be found 

 for placing others of the class in the same 

 position ? Attempts are being made in this direc- 

 tion. All eyes throughout the civilized world are, 

 indeed, at the present moment fixed upon the 

 work of Pasteur in Paris with reference to hydro- 

 phobia. It would be a great achievement for this 



