THE PEAR 173 



intrusion of the germs, rather than to depend on 

 killing them after they appear, so the orchardist 

 must hope to find a means of preventing the 

 blight instead of being obliged to practice such 

 heroic and wasteful curative measures. 



One measure looking to this end that has been 

 suggested is the destruction of old hawthorn and 

 wild crab apple trees and abandoned pear and 

 apple trees in the neighborhood of the orchard, 

 since a single infected tree would prove a source 

 of danger to every tree within a radius of a mile 

 or more. 



Such measures are important ; but they do not 

 go to the root of the matter. 



The real solution must come through making 

 the tree immune to the attacks of the germ. This 

 is the keynote of preventive medicine with the 

 human subject to-day, as illustrated by the 

 vaccine treatment, of which the most familiar 

 example is inoculation for the prevention of 

 typhoid fever. It is at least within the possi- 

 bilities that a not dissimilar inoculation may 

 give the tree immunity by developing its powers 

 of resistance, quite as the human subject is given 

 immunity. 



Of course the tree has no arterial system that 

 can be inoculated with hypodermic syringe as the 

 human subject is inoculated. But the life of the 



