SILK-WORMS. 
27 
of the silk does not solely depend on the food, but 
also on the degree of temperature in which the 
silk- worm has been reared. 
As there are mulberry-trees of different quali- 
ties, it might be imagined that these differences in- 
fluenced the state of the silk-worms. There are 
five different substances in the mulberry : 1st. 
The solid, or fibrous substance. 2d. The colour- 
ing matter. 3d. Water. 4th. The saccharine 
substance. 5th. And the resinous substance. 
The fibrous substance, the colouring matter, and 
the water, excepting that which in part composes 
the body of the silk-worm, cannot be said to be 
nutritive to the silk-worm. 
The saccharine matter is that which nourishes 
the insect, that enlarges it, and forms its animal 
substance. 
The resinous substance is that which, separating 
itself gradually from the leaf, and attracted by the 
animal organization, accumulates, clears itself, and 
insensibly fills the two reservoirs, or silk vessels, 
which form the integral parts of the silk-worm. 
According to the different proportions of the ele- 
ments which compose the leaf, it follows that 
cases may occur in which a greater weight of 
leaf may yield less that is useful to the silk-worm, 
as well for its nourishment, as with respect to the 
quantity of silk obtained from the animal. 
Thus the leaf of the black mulberry, hard. 
