20 



been proved, on dissection of the silk-worms which thus 

 suffer and become torpid through cold, that the gluti- 

 nous matter in their silk reservoirs had become so con- 

 ^e^led and tenacious, from cold, as to resemble strong 

 tendons ; which sufficiently accounted for the inability 

 of the insect to draw forth the silken filament. Yet no 

 sooner is the temperature increased, than they will re- 

 sume their labors with increased activity; but will again 

 desist, if exposed again to cold. If neglected at this 

 critical period, they assume in due time, the chrysalis 

 form, but for want of sufficient strength, leave incom- 

 plete their silken tomb. 



Many persons have erroneously imagined, that light 

 is injurious to the silk-worms : but the very reverse of a 

 belief so contrary to nature, is evidently true. In its 

 native state, it is of course habituated to the most per- 

 fect light. Indeed a due proportion of the reviving 

 light of day has been found essentially necessary to its 

 perfect health. In the perfect light of day, the leaves 

 of the mulberry and other trees exhale vital air, or that 

 pure, aetherial substance which, by being inhaled, gives 

 life and heat to the animal system, and fuel to flame; 

 while in the darkness they evolve mephitic air, which is 

 destructive and incapable of affording nourishment either 

 to life or to flame. 



Although the silk-worm will endure a great degree of 

 heat, yet when this heat is combined with excessive 

 moisture, the effect appears to be at least as deleterious 

 to the insects as mephitic air. If a silk-worm be con- 

 fined in a close vessel surcharged with moisture, and 

 heated to 88 deg. or 90 deg., it will soon reject food, and 

 shew strong symptoms of distress. The muscles will 

 soften, and evaporation will become obstructed : the 

 power of contraction which resides in the skin, and 

 which governs the secretions which are indispensably 

 necessary to its existence, will cease, and it will shortly 

 perish : while a warm-blooded animal, if sufficiently 

 supplied with pure atmospheric air, will endure an equal 



