NEUROLOGY.
This illustration shows where the brain, spinal canal and the principal
nerves of the horse are located.
STUDY OF THE NERVES.--The nervous system is a very important set of
organs controlling the motion of the various members of the body and
supplying the different senses of feeling, seeing, hearing, smelling
and tasting. The two principal organs of the nervous system are the
brain and spinal cord.
The brain is the center of the whole nervous system, and is situated in
the cranial cavity, surrounded by three delicate membranes, the outer
one being attached to the inner wall of the bones forming the brain
cavity. The brain contains several important nerves called cranial
nerves, which are given off from the brain and pass down through the
various foramen or openings in the head to supply the different organs
situated there. The optic nerve passes down to the eye, giving the
sense of sight. The auditory nerve passes down to the drum of the ear
to give the sense of hearing. The olfactory nerves, which give the
sense of smell, are situated in the mucous membrane lining the nose.
The nerves passing down to the tongue give the sense of taste. Other
nerves pass down to the lips, teeth, mouth and face, giving motion and
feeling to the parts mentioned. Others pass down to the pharynx or
gullet, giving it the power of swallowing.
The spinal cord passes from the brain through the openings in the
bones of the back, which gives off numerous small nerves that supply
the muscles of the back with motion and feeling. Nearly opposite the
shoulder blade the spinal cord gives off a large trunk of nerves,
portion of which supplies the heart and lungs with nervous power.
This is a point of importance, for if the spinal cord becomes injured
in front of these nerves immediate death is the result. The other
portions of this trunk of nerves supply the shoulder, chest and muscles
of the front legs. Passing backward along the spinal cord is found the
sympathetic system of nerves, which go to supply the bowels, stomach,
liver, kidneys, and other organs situated in the abdominal cavity.
Coming backwards along the spinal cord to about opposite the hip bones,
is another set of nerves, one of which goes to supply the rectum, or
back bowels. Others go to the generative and urinary organs where they
assist in performing their functions. Other nerves pass to the small
organs situated in the pelvic cavity; some of these nerves pass down to
the hind legs, supplying them with nervous power. The remainder of the
nerves go to supply the tail.
The difference between the nervous system of a horse and other animals
is not worth mentioning.