LUTHER BURBANK 



tion of corrosive sublimate, one part to the thou- 

 sand. 



It is merely antiseptic surgery applied to the 

 tree to combat a microbe closely similar to the 

 ones that are man's most malignant enemies. 



But, of course, such measures as these, how- 

 ever necessary, can by no means be regarded as 

 solving the problem of the pear blight. Just as 

 the surgeon of to-day attempts to prevent the in- 

 trusion 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 hawthorne and 

 wild crab apple trees and of 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 



[130] 



