externally coated with a firmly adhering layer of flat overlying
scales, with not very even upper edges, as you see. The upper or free
edges of these scales are all directed towards the end of the hair, and
away from the root. But when you look at a hair in its natural state you
cannot see these scales, so flat do they lie on the hair-shaft. What you
see are only irregular transverse lines across it. Now I come to a
matter of great importance, as will later on appear in connection with
means for promoting felting properties. If a hair such as described,
with the scales lying flat on the shaft, be treated with certain
substances or reagents which act upon and dissolve, or decompose or
disintegrate its parts, then the free edges of these scales rise up,
they "set their backs up," so to say. They, in fact, stand off like the
scales of a fir-cone, and at length act like the fir-cone in ripening,
at last becoming entirely loose. As regards wool and fur, these scales
are of the utmost importance, for very marked differences exist even in
the wool of a single sheep, or the fur of a single hare. It is the duty
of the wool-sorter to distinguish and separate the various qualities in
each fleece, and of the furrier to do the same in the case of each fur.
In short, upon the nature and arrangement and conformation of the scales
on the hair-shafts, especially as regards those free upper edges,
depends the distinction of the value of many classes of wool and fur.
These scales vary both as to nature and arrangement in the case of the
hairs of different animals, so that by the aid of the microscope we have
often a means of determining from what kind of animal the hair has been
derived. It is on the nature of this outside scaly covering of the
shaft, and in the manner of attachment of these scaly plates, that the
true distinction between wool and hair rests. The principal epidermal
characteristic of a true wool is the capacity of its fibres to felt or
mat together. This arises from the greater looseness of the scaly
covering of the hair, so that when opposing hairs come into contact, the
scales interlock (see Fig. 9), and thus the fibres are held together.
Just as with hair, the scales of which have their free edges pointing
upwards away from the root, and towards the extremity of the hair, so
with wool. When the wool is on the back of the sheep, the scales of the
woolly hair all point in the same direction, so that while maintained in
tha