SILK-WORMS. 
81 
to economize the leaves ; because, when an exact 
sufficiency of food is given to the worm, it eats 
with greater relish, digests well, and is strong. 
An object of great use in the art of rearing silk- 
worms is to contrive to obtain the greatest pos- 
sible quantity of fine cocoons, with the least 
quantity of leaves. In managing upon this prin- 
ciple, the more leaves there] are the greater will 
be the proportion of cocoons, and consequently 
the greater the profit. 
I do not exaggerate when I say, that in many 
laboratories there is a quarter, nay, a third more 
of the leaf consumed than is required ; which is 
not only a waste of leaves, but is the origin of 
many inconveniences which assail the silk- worm, 
as we shall shew hereafter. The cares which the 
silk-worm requires in its four first ages are neither 
numerous nor puzzling ; although it is in those 
ages, and particularly in the two first, that the 
strength of their constitution is formed, upon 
which the ultimate success depends. 
The silk-worm seems doomed by its natural 
constitution to have but few days of vigour from 
its coming forth, until after its fourth moulting. 
It is only healthy in the periods between the 
moultings. The two first days after it has cast 
its skin it eats sparingly ; it then becomes vora- 
cious ; this hunger soon diminishes, and even 
ceases. These phenomena occur in every moult- 
e 5 
