DISEASES OF SILKWORMS, 147 
soften, and contraction cease. In a short time 
evaporation will be obstructed, the secretions in- 
dispensable to vitality, which are effected in this 
animal by means of contraction,* will be suspended, 
and erelong it will perish, A warm-blooded ani- 
mal, on the contrary, if sufficiently supplied with 
pure air, can live without any suffering, and per- 
form all its functions without inconvenience, in such 
a temperature, whatever he the attendant degree 
of moisture. This proves how different is the 
structure of these two classes of animals.” 
Silkworms are said to be extremely sensible of 
certain odours, and to be easily affected by them. 
Tobacco has been ascertained to be a deadly poison to 
silkworms. Ifa few grains ofsnuffis thrown on them, 
immediate pain seems to be felt, from the writhing 
of the animal; in about a minute convulsions will 
ensue, and death speedily follows. Before the cat- 
erpillar expires, it ejects from its mouth a watery 
liquid ; and should another larve be touched with 
this fluid, it is certain to prove fatal. 
There is a disease to which silkworms are very 
liable in the south of France, which is called the 
jaundice, from the yellow colour exhibited hy the 
animal while labouring under the malady. This 
* The skin of the silkworm has so great a power of contrac- 
tion, that, on being cut through, it shrinks in the manner of an 
elastic substance that has been drawn out. 
