excrescences
of animals--a structure which includes horns, hoofs, hair,
feathers, and all similar appendages in different orders of
animals. This structure displays infinite diversities in colour,
constitution, and organization, and is the most variable tissue on
the whole body. Many different opinions have, however, been lately
maintained, and much research has been made, as to the nature and
texture of the parts on which the variety of colour depends."

The ancient anatomists, it appears, recognised only two parts of the
skin--the true skin, and the outer cuticle or epidermis. Malpighi
discovered a third layer interposed between these, consisting of a sort
of network, thence called _rete mucosum_, and believed to be the seat of
colour in the negro. Albinus showed this to be a continuous layer, and
not a network. Cruikshank discovered four layers--three membranes, and
the fourth a layer of colour. Flourens, at a more recent period, made
the number of intermediate layers five, four of which he showed to the
French Academy; one of these, a mucous membrane underlying the pigment,
is, according to this anatomist, a distinct organized body, existing
only in men of dark colour, and entirely wanting in the white races, or
else (which appears the more probable conjecture) maceration, and the
ordinary process of examination, fail to detect it in the skin of white
men. Lastly, the microscopical researches of Henle, Purkinje, and
Schwann, go to prove that the outer integument does not consist of
separate membranes, but is of a cellular structure, and that of these
cells or "cytoblasts," there are three distinct kinds. We will not
further analyse the different opinions as to the texture of the skin and
position of the colouring material; it certainly throws no
inconsiderable degree of doubt over certain classes of scientific
investigation, to find each subsequent research entirely altering, and
in some cases overturning, the previously received views.

To the different characters of human complexion, Dr Prichard gives three
distinctive terms--the _melanous_ or brunette; the _xanthous_ or blonde;
and the _leucous_ or albino; the _melanous_ predominating in the
southern countries, the _xanthous_ in the northern. It is observable
here, that although the natural divisions of territory with respect to
complexion, (supposing climate to have the principal modifying effect
upon complexion,) would be th