328 
THE ART OF REARING 
/ 025 . 
1000 ounces of perfect cocoons composed of living’ 
chrysalides 842 
Of the remains or envelopes cast by the worms 
when they become chrysalides . . . . 4§ 
Of pure cocoon 1501 
Total . . 1000 
Each healthy cocoon proceeding from a well- 
managed laboratory contains the seventh part, and 
even of pure cocoon, when compared to the 
weight of the cocoon containing the chrysalis. 
However, the fact is, the average quantity of 
the cocoon obtained by the silk-mill is about ^ of 
spun-silk, or 140 ounces of perfect cocoons, while 
the healthy chrysalides, which contain about twen- 
ty-one ounces of pure cocoon, will generally only 
produce twelve ounces of silk. 
Let us now connect the facts I have stated. 
About 97 pounds 8 ounces of mulberry leaves, 
will produce pounds of cocoons ; that 1 \ pounds 
of cocoons containing the healthy chrysalides yield 
about 18 ounces of pui’e cocoon; that these 
18 ounces of pure cocoon only give eight ounces 
of spun silk. 
The proportion, then, between the weight of the 
mulberry leaves and that of the pure cocoon, is 
something about 87 to 1 ; and the proportion of 
the weight of the mulberry leaf and that of the 
spun silk, is of 152 to 1. 
