38 
veals the parasites ordinarily attending putrefaction, chief among 
which is a bacillus, seen sometimes with and sometimes without a bright 
nucleus. There also exists a special form of ferment, not unlike that 
which accompanies the formation of vinegar (Mycoderma aceti Pasteur), 
which is found in short chains, the links of which are almost spherical 
Fic. 23.—Chain ferment, taken from the stomach of a flaccid chrysalis. Magnified 400 times (after 
Pasteur). 
in form (Fig. 23).* These two parasites are sometimes found together 
and sometimes separately. When the bacillus is abundant death quickly 
follows its appearance, and the disease, spreading rapidly, will some- 
times destroy a whole school ina single day. At times this bacillus 
appears so short a time before the spinning of the cocoon that the 
worms are able to mount into the branches, and even make their cocoons 
and become chrysalides. Then, however, the disease overcomes them, 
and their putrefaction produces foul cocoons. This case is, however, 
more rare, and in general the bacillus is not often found in the chrysalis. 
When the ferment alone appears the disease progresses differently. 
The worms then show the same languor on the approach of the spinning 
period, and the same indisposition to make their cocoons; but even 
then they mount the branches, perform their work of spinning, are 
transformed into chrysalides, and these into moths which may have a 
fine appearance. The silk crop may even be exceptionally good; but 
where this state has existed, when the worm has been without its usual 
 *The distance from center to center of the links of these chains is about 
1 « (=0.001"™—0.00004 inch). 
