Joined to this is the medulla oblongata. This is the lowest part of the brain and is the connecting link between the brain and the spinal cord. The medulla controls the circulation, respiration, and deglutition (swallowing).

Closely adhering to the brain, is a delicate membrane, sinking into the convolutions, and following the surface of the brain valleys throughout. This membrane is called the pia mater. In it is found the capillaries, which supply the brain with its nutritive blood in life and with embalming fluid after death. These capillaries do not penetrate the substance of the brain, but the process is one of osmosis, absorption or transfusion. Covering the outer most part of the brain, and closely adhering to the cranial bones is a dense, tough, glistening, membrane, called the dura mater. In the dura mater is found the sinuses of the brain.

In between the pia mater and the dura mater is a delicate double membrane forming a closed sack, called the arachnoid membrane. This sac contains a serous fluid, which offers great protection to the brain. These same three membranes also cover the spinal cord, and are called all together the meninges of the brain and cord.

The brain is composed of white and gray matter. The gray matter is on the outside, and the white matter is on the inside.

The spinal cavity is formed by the bones of the vertebral column. In this spinal cavity is found the spinal cord. It is cylindrical and usually about seventeen inches in length, and extends from the medulla oblongata, to the lower border of the first lumbar vertebra, where it terminates in a slender filament of gray substance.

There originate from the under surface of the brain twelve pairs of nerves, as follows:

There originate from the cord thirty-one pairs of nerves, as follows:

Cervical region8pairs.
Thoracic region12“
Lumbar region5“
Sacral region5“
Coccygeal region1“
—
31“

The circulation of the blood through the brain will be taken up later.