1.Have you ever looked carefully at a rabbit when your mother has got one in from the butcher for your dinner？If so，you may have noticed that，when the skin is removed，the red muscles can be easily seen on the body and limbs of the animal.If you separate carefully the muscles that lie along the back of the hind leg，you will see a little white thread running down the leg.This is a nerve，the largest nerve in the whole body，and it is known as the sciatic nerve.We have a similar nerve in our bodies；and when it becomes inflamed，it causes the painful disease called sciatica .
2.If you follow this nerve down the rabbit‘s leg，it will be seen to branch again and again，some of the little twigs passing to the skin，and others to the muscles of the limb.If you trace the nerve upwards into the body，which is not so easy，it will be seen to pass into the backbone.The backbone consists of a string of bones forming a hollow tube，which is filled with a long cord of soft white material.In the head this cord expands into the brain.A great many other nerves leave the spinal cord on both sides and pass to the body and the limbs，and some twenty more pass from thebrain to the head and such parts as the eyes，the nose，and the ears.
3.Small as these nerves are-some of them thinnerthan the thinnest thread-the microscopeshows thateach of them is composed of hundreds，sometimes thousands，of microscopic threads closely packed side by side，and bound together by material of very great delicacy.The nerves，then，form a system of cords joining the brain and spinal cord with all parts of the body，and this system is very much alike in the human body and in that of the higher animals.
4.You may ask，what is the use of all this？and in order to explain its use，I shall give you anillustration.You all know whatthe telegraph is.Now，the nervous system is of much the same use to the body as the telegraphic system is to Great Britain.When a ship touches at any port，the news is wired to London；andif a foreign force were to attempt a landing in time of war，the message to London would be followed by other messages sent to all parts of the country，callingthe people to arms.So，in like manner，when anything touches the human body-a pin point，or even the rubbing of our clothing-the tiny nerves convey their messages to the spinal cord and the brain ；and not till then do we feel the prick or the touch.When a flash of light falls upon the eye，or when sound breaks upon the ear，the tiny nerves are affected，and send their messages to the brain；and then，but not till then，do we see or hear.
5.We know，too，that something else may follow or accompany our feeling.The flash of light may cause us to start.The sound of the word “Attention”will cause all the soldiers in a company to draw their heels together and to hold themselves erect.In these cases the movement that is made is due to messages conveyed from the brain and spinal cord through the nerve threads to the muscles of the body，which then move as directed.We see，then，that the brain and spinal cord are like a great central telegraph office，where messages are received and dispatched，and that the nerves are like the telegraph wires.
6.But the brain has many other uses than those I have described.It is the seat of memory，the storehouse of the feelings and thoughts of our past lives.By means of the brain we are able to think，and to compare one thing with another.Doctors tell us that，when certainportions of the brain are diseased or injured，the patient may have large parts of his past life blotted out from memory，or that the powers of his mind may be so injured or destroyed that speech and thought are impossible.
7.Like all other parts of the body，the brain re-quires rest，and this it should obtain for eight or nine hours every night.When we are asleep，no sound should disturb us.Without this sleep，the greatest fatigue ensues，and the weariness and discomfort become at last unbearable.
8.Although we have learned something regarding the uses of the brain，we shall never be able to explain everything concerning it.Here，as everywhere else，we find that the more we know，the more there is to be known.People who study a great deal always should be，and generally are，the most modest and the most ready to acknowledge their ignorance.The reason is，that they most fully understand how small is man’scapacityfor acquiringknowledge，how short is hislife，and yet how vast is the material upon which he has to work.