166 PRACTICAL FORESTRY 
saplings are bent to the ground and broken, limbs are 
ripped from the trunk, and trees of considerable size, 
especially balsams and spruce, are either broken and 
split, or uprooted. The amount of devastation thus 
caused is often immense. 
3. Protection against Insects.—In the case of fire 
and destructive atmospheric agencies, the danger is 
more or less from without. In many instances it is 
entirely beyond the control of man. All that can be 
done in such cases is to institute preventive measures. 
An ounce of prevention in the case of fire, for in- 
stance, is worth a ton of cure. In the case of many 
great conflagrations which have occurred in this coun- 
try, human efforts in the way of extinguishment have 
accomplished comparatively little. 
Aside from these exterior destructive influences, 
some of the insects and other animals, fungi, or weeds 
of the forest itself, may, for some reason or other, 
become abundant and destructive. This is usually 
caused by a disturbance in some way of the equi- 
librium of the forest. 
There are many disturbing influences at work 
which are constantly causing a readjustment of the 
neighborly relations of the denizens of the forest. 
The introduction of a new species of animal may occa- 
sion a complete readjustment. The mongoos was 
introduced into Jamaica to kill the rats. Almost 
