of Russia
razed the citadel, and in this ruinous condition it was handed over to
the Walachians. Braila was the spot chosen by the Russian general
Gorchakov for crossing the Danube with his division in 1854. On the
banks of the Danube, a little above the city, are some remains of the
piles of a bridge said by a very doubtful tradition to have been built
by Darius (c. 500 B.C.).

BRAIN (A.S. _braegen_), that part of the central nervous system which in
vertebrate animals is contained within the cranium or skull; it is
divided into the great brain or cerebrum, the hind brain or cerebellum,
and the medulla oblongata, which is the transitional part between the
spinal cord and the other two parts already named. Except where stated,
we deal here primarily with the brain in man.

1. ANATOMY

_Membranes of the Human Brain._

[Illustration: Fig. 1.--Dura Mater and Cranial Sinuses.

1. Falx cerebri.
2. Tentorium.
3,3. Superior longitudinal sinus.
4. Lateral sinus.
5. Internal jugular vein.
6. Occipital sinus.
6'. Torcular Herophili.
7. Inferior longitudinal sinus.
8. Veins of Galen.
9 and 10. Superior and inferior petrosal sinus.
11. Cavernous sinus.
12. Circular sinus which connects the two cavernous sinuses together.
13. Ophthalmic vein, from 15, the eyeball.
14. Crista galli of ethmoid bone.]

Three membranes named the _dura mater, arachnoid_ and _pia mater_
cover the brain and lie between it and the cranial cavity. The most
external of the three is the _dura mater_, which consists of a cranial
and a spinal portion. The cranial part is in contact with the inner
table of the skull, and is adherent along the lines of the sutures and
to the margins of the foramina, which transmit the nerves, more
especially to the foramen magnum. It forms, therefore, for these bones
an internal periosteum, and the meningeal arteries which ramify in it
are the nutrient arteries of the inner table. As the growth of bone is
more active in infancy and youth than in the adult, the adhesion
between the dura mater and the cranial bones is greater in early life
than at maturity. From the inner surface of the dura mater strong
bands pass into the cranial cavity, and form partitions between
certain of the subdivisions of the brain. A vertical longitudinal
mesial band, named, from its sickle shape, _falx cerebri_, dips
between the two