148 
THE ART OF REARING 
repeating the fumigation, the quantity of oil of 
vitriol poured into the large bottle may be dimi- 
nished. The stated quantity of ingredients will 
be sufficient for a laboratory of five ounces of eggs. 
The bottle may be left open an hour or two in 
the last days of the fifth age of the silk-worms; 
and placed here and there in the laboratory, and 
■even on the corners of the wicker hurdles, to dif- 
fuse the vapour thoroughly. 
5 This remedy may be employed whenever on 
going into the laboratory the air appears to have 
an unpleasant effluvia, and that there is any close- 
ness, or difficulty of breathing. 
1st. It may take place when the litter of the 
silk- worm is removed, particularly in the fifth age. 
2d. When in damp weather the air of the labo- 
ratory continues damp, even after having made 
the blaze, which renders the fermentation still 
quicker. 
e This fumigation may be of use also towards the 
end of the fourth age, if the air were perceived to 
be impure. I, however, never needed it, until after 
the fourth age of the silk-worms, and at the be- 
ginning of the fifth age. I use a fumigating appa- 
ratus much more convenient than the bottle, and 
which I shall describe in Chapter XIII., among the 
utensils required in the laboratory. 
If there are several small fire-places in the labo- 
ratory, and that b es are frequently made in 
