126 
THE ART OF REARING 
Those who attend silk-worms should breathe 
as freely in the great laboratory as in the open 
air; they should feel no difference but that in the 
heat of the interior temperature, and the latter in 
temperature, not in the closeness. 
Therefore, should the air appear heavy, the 
fire of straw, or shavings, ought to be lighted, to 
renew the air, which is done in a moment. 
In my laboratories, the interior air is more 
pleasant than the exterior air, from the delightful 
smell of the mulberry leaves. 
In proceeding as I have described, the silk- 
worms will breathe continually a pure and dry 
atmosphere, which makes them most healthy. 
We shall see in Chapter XIII., that the con- 
struction of the laboratories should be such, that 
any unforeseen occurrence that may arise to ob- 
struct the necessary operations can be easily 
remedied. 
CHAPTER VII. 
OF THE REARING OF THE SILK-WORMS IN THE 
FIRST PERIOD OF THE FIFTH AGE, OR UNTIL 
THE MOMENT WHEN THEY PREPARE TO RISE 
ON THE EDGES. 
The fifth age of the silk-worm is the longest, 
and most decisive. It requires the knowledge of 
the philosopher as well as the care of the practi- 
