SILK-WORMS. 
197 
2nd. And if after two or three days, the silk- 
worms, that are reduced to 10 quintals and 50 
pounds weight, are changed into 600 pounds 
weight of cocoons, it is evident, that in three or 
four days they must have lost 450 pounds weight 
of substance, either in liquid, or in vapour and gas. 
3rd. In the space of six or seven days, therefore, 
the bodies of the insects requisite to produce only 
600 pounds of cocoons, must have lost 700 pounds 
weight of vapour or gas, solid and liquid excre- 
mental substance ; this astonishing quantity of sub- 
stance, excreted from the bodies of the silk-worms 
in so short a time, is of greater weight than the 
total weight of the cocoons and aurelias, which only 
weigh 600 pounds. It is scarcely credible that 
the bodies of the silk-worms should yield so much 
noxious matter in a few days, were it not demon- 
strated by positive facts. (Chap. XIV.) 
It is needless to remark how much this large 
body of exhalation, were it stagnant in the labo- 
ratory, might, in the latter days, generate disorders 
and disease most quickly, and cause great mor- 
tality at the very moment when the abundant crop 
of the cocoons was most confidently expected. 
We must, therefore, feel the deep necessity of at- 
tentively following the prescribed directions for 
avoiding this evil. 
K 3 
