SILK-WORMS. 
263 
weight they acquire, devour a quantity of vege- 
table substance, which, as we remarked, abounds 
in liquid, and in substances of which the worm 
must disencumber itself. 
This is what happens : — This insect has pro- 
perly neither lungs nor urinary organs. The only 
remaining means left it, besides the intestinal 
tube, is therefore cutaneous transpiration. It can 
well evacuate by this means the liquid, and alka- 
line, and acid substances which are in a dissolved 
and suspended state ; but not having the faculty 
of discharging by urine jDOSsessed by herbivorous 
domestic animals, there remains in the body of the 
silk-worm a portion of the earthy particles taken 
in with its food, which insensibly accumulate; of 
which we have the proof in the acid and alkaline 
earthy substances which the animal evacuates 
when it has attained the moth state. From this 
there results, that when by want of care the tran- 
spiration of the insect is checked, there are certain 
chemical attractions formed within it, as yet but 
imperfectly understood. It is to these attractions 
that should be attributed the various diseases of 
the fifth age, commonly denominated in Italian 
segno, calcinaccio, and negrone, and other simi- 
lar disorders, which are produced by modifications 
of the same general causes that I have before 
stated. 
The disorder called the segno results from the 
