Restoration of the Silkworm. 159 
who have not watched the interesting changes which take place in 
the larvae of the Bombyx Mori, or common silkworm, from the 
point of its exit from the egg until it has reached its full butterfly 
existence ; and many there are who have been sadly disappointed 
at the mortality which comes over a brood of silkworms in a 
single night from some cause or causes unknown, and conse- 
quently irremediable. Such epidemics are continually occurring 
in China as well as Europe, and constitute one of the greatest 
obstacles to the introduction of the culture of the silkworm into 
England. What occasions this sudden decimation of these insects 
has never been determined, but has long led to a wish, on the 
part of those interested, that a more hardy breed of silk-producing 
worms could be introduced into Europe, even though the produce 
was coarser and of a worse colour than the ordinary mulberry 
silk.”* Here, then, is a further and very recent testimony to the 
diseased state of the worm. 
Good Quality of the Silk no Proof of general Health. 
I shall doubtless be told that “the proof of the pudding is in 
the eating,” and that as silk of the best quality and worth twenty- 
five shillings per pound has been produced in the Punjab, the 
worm cannot possibly be diseased or have lost its constitution. 
To this I reply, that in order to test “the pudding” properly 
and fairly, we require a judge possessed of some knowledge of 
what a pudding ought to be. 
In the introductory remarks to my “‘ Monograph on the Genus 
Attacus,” | have shown, after Kirby and Spence and other autho- 
rities, that the gum from the reservoirs being conveyed to the 
mouth by the constriction of certain muscles, passes through two 
small orifices in the lip, and the two fibres thus formed, being taken 
up and twisted together by the hook-like processes in the mouth 
appointed to that office, become one fibre of silk on coming into 
contact with the cold external air. Now these two orifices in the 
lip are expressly appointed to the purpose of regulating the thick- 
ness of the silken fibre with which the cocoons are formed; they 
are a provision of Nature which determines the thickness of the 
silken thread, and that thickness, in worms of equal size, will be 
constantly uniform, so that a large and healthy worm will yield a 
thicker fibre than a smaller and degenerated worm. 
As long as the reservoirs contain gum, the thickness of the silk 
will be the same whether the worm is diseased or not, provided 
* Journal Soc. Arts, Nov. 6th, 1863, p. 776, 
