CHAPTER IV. 
THE NERVOUS SYSTEM. 
THIS system is a very important set of organs controll- 
ing the motion of the various members of the body 
and supplying the different senses of feeHng, seeing, 
hearing, smelling and tasting. The two principal 
organs of the nervous system are the brain and the spinal 
cord. 
1. The Brain. — The brain is the centre of the whole ner- 
vous system, and is situated in the cranial cavity, surrounded 
by three delicate membranes, the outer one being attached 
to the inner wall of the cranial cavity. It contains several 
important nerves called the cranial nerves, which are given 
off from the brain and passed down through the various 
foramen or openings in the head to supply the different or- 
gans 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 
aulfactory 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 gullet or pharynx, giving it the power of swallowing. 
2. The Spinal Cord. — Passing from the spinal cord, which 
is situated in the opening of the bones of the back, are 
numerous small nerves to supply the muscles of the neck, 
giving it motion and feeling. Nearly opposite the shoulder 
blade, or withers, the spinal cord gives off a large bunch 
of nerves, part 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 imme- 
diate death is the result. The other part of this bunch of 
nerves supply the shoulder, chest, and muscles of the front 
legs. Passing backwards 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 a.bdominal cavity. Continuing backwards along the 
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