re between this lobe and
D, the occipital lobe;
E, cerebellum;
F, arbor vitae;
H, pons Varolu;
K, medulla oblongata;
L, portion of lobe on the opposite side of brain.

The white curved band above H represents the corpus callosum.]

Disease or injury of the cerebellum usually produces blindness,
giddiness, a tendency to move backwards, a staggering, irregular gait, and
a feeling of insecurity in maintaining various positions. There is no loss
of consciousness, or other disturbance of the mental functions.

269. The Membranes of the Brain. The brain and spinal cord are
protected by three important membranes, known as the meninges,--the
dura mater, the arachnoid, and the pia mater.

The outer membrane, the dura mater, is much thicker and stronger than
the others, and is composed of white fibrous and elastic connective
tissue. It closely lines the inner surface of the skull, and forms a
protective covering for the brain. Folds of it pass between the several
divisions of the brain and serve to protect them.

The arachnoid is a thin membrane which lies beneath the dura mater.
It secretes a serous fluid which keeps the inner surfaces moist.

The pia mater is a very delicate, vascular membrane which covers the
convolutions, dips into all the fissures, and even penetrates into the
interior of the brain. It is crowded with blood-vessels, which divide and
subdivide very minutely before they penetrate the brain. The membranes of
the brain are sometimes the seat of inflammation, a serious and painful
disease, commonly known as brain fever.

270. The Medulla Oblongata. This is the thick upper part of the
spinal cord, lying within the cavity of the skull. It is immediately under
the cerebellum, and forms the connecting link between the brain and the
spinal cord. It is about an inch and a quarter long, and from one-half to
three-fourths of an inch wide at its upper part. The medulla
oblongata consists, like the spinal cord, of columns of white fibers
and masses of gray matter, but differently arranged. The gray matter is
broken up into masses which serve as centers of origin for various nerves.
The functions of the medulla oblongata are closely connected with the
vital processes. It is a great nerve tract for transmitting sensory and
motor impressions, and also the seat of a number of centers for reflex
actions of the highest importance to life. Through the posterior part of
the medulla the sensory impressions pas