BOMBYCIDJE. 131 
of tlie gum which the insect uses in forming it. 
Warm water, which is found sufficient in the case 
of the common silk-worm, has in most instances 
no perceptible effect on it ; nor, in fact, any solvent 
that has yet been tried. The silk, therefore, can 
be made available only in an imperfect way, by 
tearing it from the cocoon and carding it like wool. 
The su])ject is well worthy the attention of che- 
mists, for the discovery of a substance which should 
dissolve the gum without destroying the texture of 
the thread, would enable us to add incalculably to 
the sources whence the finest silk may be derived. 
Perhaps a hint miglit be taken on this point from 
the fact that the insect itself is provided with a 
fluid which dissolves the gum, and which it employs 
for the purpose of opening a passage for itself when 
emerging from the cocoon. Could a portion of this 
substance be obtained and subjected to analysis, the 
ingredient to which it owes its solvent quality might 
be detected. In some cases it is discharged in great 
aJjun dance. 
