The history of silk, cotton, linen, wool, and other fibrous ... - Cd3wd.com

140 CULTIVATION AND MANUFACTURE OF SILK.
Plate IV. ; this figure shows the garden spider {Epeira diadema)
suspended by a thread proceeding from its spinneret.
We have seen tliat the thread of the silk-worm is composed
of two filaments united, but the spider's thread would appear,
from the first view of its five spinnerets, to be quintuple, and in
some species which have six teats, so many times more. It is not
safe, however, in our interpretations of nature to proceed upon
conjecture, however plausible, nor to take anything for granted
which we have not actually seen ;
since our inferences in such
cases are almost certain to be erroneous. If Aristotle, for exam-
ple, had ever looked narrowly at a spider when spinning, he
could not have fancied, as he does, that the materials which it
uses are nothing but wool stripped from its body. On looking,
then, with a strong magnifying glass, at the teat-shaped spin-
nerets of a spider, we perceive them studded with regular rows
of minute bristle-like points, about a thousand to each teat,
making in all from five to six thousand. These are minute
tubes which we may appropriately term spinnerides, as each
is connected wdth the internal reservoirs, and emits a thread
of inconceivable fineness. Fig. 9. represents this wonderful
apparatus as it appears in the microscope.
We do not recollect that naturalists have ventured to assign
any cause for this very remarkaljle multiplicity of the spinner-
ules of spiders, so different from the simple spinneret of caterpillars.
To us it appears an admirable provision for their mode
of life. Caterpillars neither require such strong materials, nor
that their thread should diy as fjuickly. It is well known in
our manufactures, particularly in rope-spinning, that in cords
of equal thickness, those which are composed of many smaller
ones united are stronger than those spun at once. In the in-
stance of the spider's thread, this principle must hold still more
strikingly, inasmuch as it is composed of fluid materials that
require to be dried rapidly, and this drying must be greatly
facilitated by exposing so many to the air separately before
their union, which is effected at about the tenth of an inch
from the spinnerets. In Fig. 10. Plate IV. each of the threads
shown is represented to contain one hundred minute threads,
the whole forming only one of the spider's common threads.