It might seem at first sight a hopeless task to search in so dense and complicated
a structure as the skin, for the analogtie of a membrane like that I have been describing,
which, in no situation where it can be unequivocally brought into view, exceeds the
8000th of an inch in thickness. But as it must exist, if at all, between the epidermis
and the vessels and nerves of the cutis, in a position sufficiently determinate, much of
the apparent difficulty is removed. The most favourable situations for its detection
are those in which the skin is highly developed, presenting, like the small intestine, villi
(termed papilla?) on its free surface. The close resemblance between these papillse and
the villi of mucous membranes has been observed by many anatomists. The distribu-
tion of the vessels within both is essentially the sanie. Here, then, under thg epidermic
layer, we might expect to find the basement membrane. I have removed with great
care the whole of the epidermis from a thin vertical section of such a specimen (and it
is better to have previously steeped it in solution of cai'bonate of potass), and have
then examined the outline of the bare papillje with a power of 300 diameters. This
outline is sharply defined, and appears to be formed by a homogeneous membrane,
enclosing the vascular and nervous contents. This membrane I beUeve to be that
which I am now describing, though, as in the case of the intestinal villi, I have never
been able to isolate it, and thus unequivocally prove its presence. This is a part of
the skin which has never been noticed by anatomists on account of its tenuity, but



BPITHELIDM.
