294 
THE ART OF REARING 
the other with the hall (a). In the centre of 
the floor there is a large square opening, which 
communicates with the lower part of the building 
(c). This is closed with a wooden folding-door, 
which may be removed at pleasure ; this aper- 
ture is used for throwing down the litter and 
rubbish of the laboratory, and is also useful for 
admitting the branches and leaves of the mulberry, 
which can easily be drawn up with a hand pulley. 
This same aperture keeps up the circulation of 
air, by moving a large column of air, when the 
three window frames at the end of the laboratory 
are open. 
I have had an interior and an exterior bell hung, 
o hasten attendance, when the orders are to be 
given or executed. 
Such is the construction of my great labora- 
tory, in which I place the silk-worms after the 
fourth casting or moulting. 
It is impossible the air should remain stagnant 
in it, or that it should ever be damp; as this 
building stands alone, the ventilator in the three 
•walls must by their exposition keep the air in the 
utmost equilibrium. Should it, notwithstanding 
all this, have a tendency to stagnation, the air 
may be instantly put in motion by establishing 
great currents of air, and burning blazing light 
fires in the six fire-places. 
