This section is from the book "Health", by W. H. Coefield.
I have mentioned the Sixth pair already; the seventh pair of nerves are called the facial nerves, because they supply the muscles of the face; they are purely motor nerves.
The eighth pair were counted as part of the seventh pair by the old anatomists, and are the nerves which go to the organs of hearing, conveying the sensation of hearing from the organs of hearing to the brain; they are called the auditory nerves, and are purely sensory.
Now, I need not go on mentioning all these nerves, but the nerves of one more pair are so important that I must speak to you about them. One pair of the nerves which rise from the medulla oblongata, leave the brain and go to other parts of the body than the head; these nerves go by the name of the pneumogastric or the vagus nerves, from their wandering course; they supply the larynx in which the voice is formed, part of the pharynx, the windpipe, the oesophagus or gullet, the lungs, and going along by the oesophagus, pass through the diaphragm and supply the stomach; they also give branches to the heart So you see that they are extremely important nerves. They go a long way, and supply important organs-the heart, the lungs, the oesophagus, the larynx, the stomach, and others, and that is one of the reasons why the medulla oblongata, from which they start, is such an extremely important part of the nervous system.
You may cut off the brain of an animal entirely, so long as you leave the medulla oblongata untouched, and he will go on living; he has no senses, but lives for some time, because this pair of nerves which supply the heart, the lungs, the stomach, etc., is left untouched.
Not only so, but fibres from all the cranial nerves, except the first two pairs, have been traced into the medulla oblongata.
The small brain has the property of co-ordinating the muscles on the two sides of the body; of causing the muscles of the body to act in concert with one another. When the small brain is injured the animal does not walk straight, but twists round and round.
The ganglia at the base of the brain are nerve centres, which are capable of acting independently of the will; they are connected with most of the nerves that belong to the brain.
Now, we know that reflex actions are capable of being performed by the spinal cord independently of the will; such actions are also capable of being performed by means of the nerves which belong to the brain. For instance, when we see a flash of lightning, or when a lighted candle is passed near to our eyes, we wink unconsciously. And not only so, but if you pass something quickly in front of a person's eyes it will make him wink; he cannot help it, even if he tries to; so that is an action which occurs not only independently of, but even in spite of, the will, and is a purely reflex action. It is produced by the stimulus travelling along the optic nerves from the eyes to the ganglia at the base of the brain, causing the sense of something coming too near the eyes, upon which these ganglia at the base of the brain immediately start a stimulus along the nerves which go to the muscles of the upper eyelids, causing these muscles to contract and pull down the eyelids; that is a reflex action performed by the brain, and entirely independently of the will of the animal, so that these ganglia at the base of the brain are capable of originating actions, movements, without our knowing anything about it.
Which, then, is the part of the brain that has to do with consciousness ? It is the grey matter on the surface of the brain. In it resides our will, and all our higher powers as animals. As we ascend in the scale of animals that grey matter becomes more and more in extent, the convolutions of the grey matter become more complicated, and it has even been distinctly shown that men of transcendent ability have been found to possess brains, not only of great weight, but with an extremely complicated surface, and so a greater quantity of grey matter on the surface of the brain; so that we have no doubt at all that the grey matter is the centre from which all the impulses which we know anything about are started, and investigations have been in progress for finding out the parts of the body controlled by the different parts of this grey matter.
A word about phrenology. By phrenology people pretend to tell you the character of a man by the examination of his skull Now, if they could examine his brain, and find out what these different parts of the brain do, there would be some sense in it, but they do it by the shape of the skull I will tell you a fact that is a very hard one for phrenologists, and that is, that there is no one part of the brain which is always underneath a fixed part of the skull; you cannot put your finger on any part of the head and say what part of the brain is under it, so that if the brain has anything to do with character, it is clear that you cannot tell a character by means of the skull There is, however, something in physiognomy; there is no doubt that a trace of character can be seen generally in the delineations of the face, and different parts of the body; and I might almost say that scientific deductions have been drawn from the study of features; but what I want to point out to you is that you can draw no conclusion as to a person's character, except in the roughest way, from bumps on his skull.
Now, I hope you have all gathered from this lecture that the nervous system is made up of a series of contrivances which consist of nerve fibres going to and from nerve centres: fibres along which stimuli go towards the nerve centres are called afferent fibres, and those along which stimuli travel from the nerve centres towards parts of the body, are called efferent fibres. The whole of the nervous apparatus of the body is made up of elements, each consisting of an afferent fibre, a nerve centre, and an efferent fibre.
When you have a reflex action it is because a stimulus has come from some part of the body to a nerve centre, which stimulus is then started (generally being communicated to other nerve centres with which that is in connection) along efferent fibres to certain muscles, which are caused to contract. That is the whole theory; it is built up entirely upon that plan.
The ganglia at the base of the brain are connected by nerve fibres with the spinal cord, and thus by the spinal nerves with different parts of the body, as well as with parts of the head by cranial nerves. Stimuli come along these nerves, and ultimately reach the ganglia at the base of the brain. Now, if a purely reflex action is produced, it is because one of these ganglia at the base of the brain sends stimuli along efferent fibres to parts that are to be moved, and the animal knows nothing about it. Such are most of the movements that I have been making during this lecture (unless when looking for a piece of chalk or a duster); they have been purely reflex actions, not natural reflex actions, because I could not have made them when I was born; they were acquired reflex actions, and performed in obedience to orders from the ganglia at the base of the brain, without my knowing anything about it When the will comes into play, it is because the ganglion at the base of the brain which receives the stimulus, sends stimuli through the white matter of the brain to the nerve centres in the grey matter on the surface of the brain, from which a stimulus is sent back to another of these ganglia, and then that ganglion sends the stimulus on to the part to be moved. Suppose I find my finger touching, by accident, the chimney of this gas-light, a stimulus is sent,- a sensation of heat is conveyed along the nerves of my arm through their posterior roots,-into the spinal cord, up the grey matter of the spinal cord to the ganglia at the base of the brain, and a stimulus is sent from the ganglia to certain muscles that move my arm; they contract, and my hand is withdrawn before I know it; but if I determine to hold it there, then the sensation comes to the ganglia at the base of the brain, and is sent from them through the white fibres to the grey matter on the surface of the brain, in which my will, somehow or other, resides, or by means of which it manifests itself; that grey matter sends a command to the ganglia at the base of the brain, to cause these muscles to still contract, and keep my hand against the hot place; that is the difference between reflex actions and the actions performed by the will; but you see that the plan of the apparatus is the same, the nervous " element * being simply doubled.
We know, for many reasons, that the higher powers,- intelligence, consciousness, will, and so on,-reside in the grey matter on the surface of the brain; if this grey matter on the surface of the brain be removed the animal loses all consciousness, and also pressure upon the grey matter on the surface of the brain causes unconsciousness. In young infants the bones of the skull do not meet together; there are spaces left where the bones are joined by membranes, and a good many nurses are in the habit, when children are peevish from indigestion or teething, of pressing their fingers on these membranes, which prevents them crying,-not because it cures the indigestion or the teething, but because it makes the children more or less unconscious, and insensible to pain.
One other thing, and that is the last. This grey matter, in which movements are originated, and sensations received and interpreted, which seems to command and arrange everything, is itself insensible.