, showing the structure of the fibre of wool and fur.
We saw that the wool fibre, of which fur might be considered a coarser
quality, possesses a peculiar, complex, scaly structure, the joints
reminding one of the appearance of plants of the _Equisetum_ family,
whilst the scaled structure resembles that of the skin of the serpent.
Now you may easily understand that a structure like this, if it is to be
completely and uniformly permeated by a dye liquor or any other aqueous
solution, must have those scales not only well opened, but well
cleansed, because if choked with greasy or other foreign matter
impervious to or resisting water, there can be no chance of the
mordanting or dye liquids penetrating uniformly; the resulting dye must
be of a patchy nature. All wool, in its natural state, contains a
certain amount of a peculiar compound almost like a potash soap, a kind
of soft soap, but it also contains besides, a kind of fatty substance
united with lime, and of a more insoluble nature than the first. This
natural greasy matter is termed "yolk" or "suint"; and it ought never to
be thrown away, as it sometimes is by the wool-scourers in this country,
for it contains a substance resembling a fat named _cholesterin_ or
_cholesterol_, which is of great therapeutical value.
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