39 
agility at the spinning time, where it has shown this apparent laziness, 
then, though the cocoons be of the firmest and the moths the finest, 
there will exist a weakness, a constitutional debility, that will show 
itself in the next generation. This is the only way in which flaccidity 
is hereditary, in this predisposition of the worm to succumb to disease 
on account of the affection which weakened but which did not kill the 
parent. 
Such are the symptoms attending flaccidity in Silk-worms, and from 
them M. Pasteur evolved the theory that the disease was caused by the 
fermentation of the food in the intestinal tube of the larva, which was 
followed by diarrhea and the closing of the anal orifice, as already men- 
tioned. Confirming this theory of food fermentation is the fact that the 
same parasite (Fig. 23) which is found in the intestines of flaccid larvee 
also exists in a fermented broth of mulberry leaves. Digestion thus 
arrested, the worm ceases to eat and becomes languid. The gases 
evolved by the processes described burst the walls of the intestines and 
cause the death of the victim. Such is the Pasteur theory, followed, as 
a rule, by the French scientists. 
Italians, on the contrary, believe with Verson and Vlacovich, who 
claim to have observed ‘that in the flaccid worm the micro organisms 
are not at times to be found; that it has been proved that in the begin- 
ning there occurs a tumefaction of the membrane of the intestines, 
and that this membrane, as the disease advances, disappears here and 
there, and finally altogether. According to them flaccidity consists 
primarily of a lesion of the membranous walls of the intestines, which 
would generally be followed by the development and multiplication of 
the micro-organisms which Pasteur considered the primitive cause of 
the disease. It is a fact, nevertheless, that all acknowledge, that in 
most cases flaccidity is accompanied by bacilli and ferments in great 
numbers in the intestinal tube.”* 
Flaccidity generally appears after some sudden change in the weather 
or temperature, as, for instance, a thunder shower, or a hot, heavy day. 
It is apt, too, to follow the feeding of wet or fermented food. If the 
Shelves go too long without cleaning and begin to mildew; if the worms 
are too crowded on the table and their natural respiration interfered 
with, flaccid subjects will soon appear in the school. These, by their 
unhealthy excrement, soil the food of their neighbors, who quickly fol- 
low them in the path of disease. It is thus that flaccidity becomes 
highly infectious. 
No very satisfactory means have been proposed for combating this 
malady when once it appears. It would be well, on the discovery of 
the first victims, to take the worms remaining healthy into another 
apartment and give them more space and plenty of air. Attentive care 
may then save the crop, though by no means with certainty. 
*Perroncito, I Parassiti, p. 35. 
