264 
THE ART OF REARING 
highest degree of chemical attraction that the 
silk-worm can endure. It is equivalent to a pe- 
techial or spotted disease, and evidently conduces 
to the decomposition of the primitive animal, and 
to the compounding of another of a nature totally 
dissimilar ; for when the acid, alkaline, and earthy 
substances have accumulated in great abundance, 
and have approximated so far as to exert that affi- 
nity termed by the chemists reciprocal affinity, the 
organic substance is speedily decomposed and dis- 
organized. There are clear proofs of their dis- 
organization in the black spots or other spots 
which appear on the body of the insect, and are 
indicative of its approaching transformation into a 
solid chemical compound ; after which the silk- 
worm hardens and dies. This disease, or decom- 
position, is never contagious*. As the check of 
* In the volume published b v M.Dandolo in 1S1G, in con- 
firmation of Ills new mode of rearing' silk-worms, he gives 
more detailed explanations of the causes of the disease 
called segno, which appears to be what in France is called 
the scarlet (les rouges). The following is an extract from 
it : — 
“ It is known that the silk-worm, like all other animals, can- 
not exist without vital air (oxygen gas), which forms the fifth 
part of atmospherical air. It is also known that all substances, 
when in fermentation, discharge a quantity of fixed or me- 
phitic air (carbonic acid) ; and wherever this acid penetrates, 
it expels vital air. 
“ This fixed air, which cannot be inhaled, is, as I said, ail 
acid that may preserve animal substances from corruption, 
when they possess some principle that combines with this 
