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 
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