272 
THE ART OF REARING 
When lying too thick on the wickers, they press 
against each other, and breathe with difficulty ; 
besides which, the transpiration is compressed ; 
the fixed air (carbonic acid) cannot evaporate from 
the insects, as it does when the insect breathes 
freely *. 
The disadvantages which I have been speaking 
of, are attributable to ill management, principally 
in the fifth age, although they may occur in the 
preceding ages, and cause the animal to become 
a receptacle of noxious substances, which contri- 
bute to breed those diseases of which we have 
hitherto treated. 
Silk-worms are generally reared in a manner 
so erroneous, that notwithstanding their natural 
strength, they must sink under such management. 
There are other disorders, called giallume 
riccione, and the soffocamento ; the two first 
are modifications of the above-described, and 
only differ in violence, or by the circumstances 
which produced them ; however, in these diseases, 
the silky substance is seldom affected f- 
* It would be very beneficial to use wicker hurdles or 
trays, without ledges or borders. As the carbonic gas, 
which is heavier than the atmospheric air, might thus escape 
as fast as it may be formed. The ledges of M. Dandolo's 
hurdles are not deep, and he no longer doubles the edge of 
the paper up, but leaves them smooth, to allow free vent for 
the carbonic gas, through the openings. — ( Translator .) 
1 1 opened several large sick silk-worms, that would inevita- 
bly have died ; and I found the silk in the two reservoirs perfect 
