On the Structure of the Membrana Tympani in the Human Ear.—
Mr. Joseph Toynbee, in a paper read at the Royal Society on the 20th
June, describes the Membrana Tympani as consisting of the following
layers, quite distinct from each other, both as regards their structure and
functions.
1.	Epidermis.
2.	The proper fibrous layer, composed of
a.	The lamina of radiating fibres.
b.	The lamina of circular fibres.
3.	Mucous membrane.
One of the principal objects of the paper is to describe the structure
and functions of the fibrous laminae. Since the time of Sir Everard
Home, who pronounced the layer of radiating fibres to be muscular,
anatomists have differed in their views of the nature of the fibrous ele-
ment of the Membrana Tympani. The lamina of radiating fibres, the
outer surface of which is covered by the epidermis, is continuous with
the periosteum of the external meatus. With the exception of the up-
permost fibres, which, on account of their being somewhat flaccid, have
been considered as a separate tissue, under the name of “ membrana
fiaccida,” the radiate layer is composed of fibres which extend from
the circular cartilaginous ring to the malleus, and they interlace in their
course. These fibres are from the 4000th to the 5000th part of an inch
in breadth.
The lamina of circular fibres consists of fibres, which are firm and
strong towards the circumference, but very attenuated towards the cen-
tre. These fibres are so attached and arranged, as to form a layer of
membrane, which, in a quiescent state is saucer-shaped. The fibres
composing the circular are smaller than those of the radiate lamina
being from the 6000th to the 10,000th part of an inch in breadth.
The facts that appear to be adverse to the idea of the fibres of either
layer being muscular, are
1.	The absence of distinct nuclei in the fibres.
2.	Their great denseness and hardness.
The four laminae forming the Membrana Tympani are continuous
with the other structures, of which they appear to be mere modifica-
tions, and not one is proper to the organ.
The tensor tympani ligament, which had not been previously noticed
by anatomists, is particularly described by Mr. Toynbee in the paper
read before the Royal Society. It is attached externally to the malleus,
close to the insertion of the tensor tympani muscle, and internally to
the cochleariform process.
The latter part of the paper is occupied by observations on the func-
tions of the fibrous lamin®, and of the tensor ligament of the Membrana
Tympani; and it is shown that by these two antagonistic forces, the
one tending to draw the Membrana Tympani outwards, the other in-
wards, this organ is maintained in a state of moderate tension, and is
always in a condition to receive ordinary sonorous undulations.—Lon-
don Journal of Medicine.