SILK-WORMS. 
237 
sides ; the mice cannot get at them, and they are 
well preserved. They must be inspected nearly 
every month. 
The eggs spoil in a moist place, and the silk- 
worms which they produce are not vigorous. 
(Chap. XII.) 
When entire broods have been lost, and the 
origin of the mischief has been examined, it has 
been easily found that the eggs had been kept in 
a damp place, which had not been supposed could 
have been the cause of the loss. 
If it is imagined that the place ill which the 
eggs are stored is not dry, it may be ascertained 
by using the barometer. 
Chapter XI. 
OBSERVATIONS ON THE VARIETIES IN SILK- 
WORMS, AND ON THE ESSENTIAL DIFFER- 
ENCE EXISTING BETWEEN THE LEAF OF THE 
GRAFTED MULBERRY TREE AND THAT OF 
THE WILD MULBERRY GIVEN TO SILK-WORMS 
OF THE SAME QUALITY. 
I have already stated (Chap. III.), that besides 
the saccharine substance of the leaf which nou- 
rishes the silk-worm, these insects also extract, by 
means of their 'peculiar organization, a resinous 
