336 
POPULAR SCIENCE REVIEW. 
perverted ; as in tlie case of a limb which has been removed, 
where, when the nerves that supphed the removed part are 
affected with pain, this is referred to the part which has been 
lost, it may be, years before. 
The functions of the skin as a covering for the body, adding 
beauty and preserving the delicate structures underneath, regu- 
lating the intensity of sensations from without, and (by a 
beautiful contrivance which we shall subsequently refer to) the 
amount of temperature within, are a further illustration of the 
multiplicity of ends attained by the Creator through one and the 
same agency ; and, though last, not least, we may mention the 
function of excretion, or removing from the body materials no 
longer of use to it, and which, if retained any longer, would 
become actually injurious to it. 
We shall now proceed to describe the beautiful structure of the 
skin, by which it is adapted for the discharge of these numerous 
and important offices. The skin is composed, as most of our 
readers are aware, of two layers ; an outer, called the cuticle, 
or scarf-skin, or sometimes termed the epidermis ; and an inner, 
called the cutis, or true skin, or sometimes the dermis. This 
latter rests upon a very fine interlaced or netted structure, called 
the areolar tissue, out of which, if we may so express it, the 
granules and fibres of the skin are formed. 
It has been usual to describe a third layer placed between the 
true skin and the scarf-skin, and called the veto mucosum, or 
pigment layer ; but later researches have shown that there is no 
such distinct layer, and that the pigment cells, to which the 
colour of the skin in different races is due, are but a different 
stage in the development of the scarf-skin. This scarf-skin is 
never of very great thickness in any animal, but the true 
skin is of very variable thickness, and is that portion of the 
skin on which depends the thickness of the hide of the pachy- 
dermatous animals, a character so remarkable as to give name 
to the class to which they belong, which includes such animals 
as the rhinoceros, hippopotamus, elephant, horse, pig, etc. In 
the whale the cutis attains the thickness of about an inch, which 
is the greatest known in any animal. 
It seems the most natural method in describing the skin to 
begin with the cuticle, which is at the surface, and so proceed 
from the better known to the less known, as in most other 
matters of knowledge. The cuticle, then, consists of several 
layers of laminated scales, the laminated form being best marked 
at the very surface, where tbe scales are constantly falling off 
as a kind of scurf, and are as constantly being renewed from 
below. These scales are formed by the flattening out of 
granules more or less rounded, which is the form assumed by 
the particles of the cuticle in its deeper layers ; these granules 
