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Human Brain as the Highest Product of Matter

July 14th, 2009 · No Comments

The most important part of the nervous system of a human being, is what may be called the new brain. It is so large, and has grown out so far in all directions, that the whole part of the old nervous system is under it. Ordinarily when we talk about a man’s brain it is entirely of this new brain that we are thinking. The proper name for it is cerebrum.

The first glance at the cerebrum shows that it is a double organ. It has a right half and a left half. These two are alike, though it seems that in right-handed people the left half, and in left-handed people the right half is slightly larger.

If we separate slightly the two halves of the cerebrum and look down between them, we see a mass of white nervous tissue running across from one side to the other. This is a bridge between the two halves of the brain by which they are made to work and act as one. When we look at the surface of the brain we see at once that it is very much folded. The folds vary in depth and length but on the whole they form a definite pattern which is the same on both sides of the brain, and its main lines are the same in all human beings.

The surface of the brain is the all-important part. The brain in the animal world increased until it has reached the size it is in the human head. This means that there has been a great deal of room required to house the brain.

Therefore the skull has also become bigger. But the brain has grown more quickly than the skull, and the surface has been deeply tucked away here and there. There is as much or perhaps, more, of the surface of the brain tucked away than shows on the outside. The higher the type of brain, the more its surface is folded. As animals have become more and more intelligent, the surface of the brain has become more folded.

When we cut through the cerebrum of any of the higher animals, we find that it consists of an outside layer which is grey and an inside layer which is white. This grey layer is often called the mantle. It is the real brain, and it is the most wonderful thing of which we have any knowledge. It owes its grey colour and all its meaning and wonder to the fact that it is principally made up not of nerve-fibres, but of nerve-cells. The rest of the brain is made up of nerve-fibres or nerves which give the inner layer a white colour. The grey mantle contains comparatively few nerve-fibres which connect its different parts.

Several layers of cells are found in any part of the grey mantle. The cells differ in different parts of the brain. When examined, corresponding parts of the brain in a large number of animals of quite different kinds show the same arrangement of cells. If a microscope slide containing a large number of cells shaped liked pyramids and arranged in a certain way were shown to an expert, he would rec¬ognize them as belonging to that part of the brain which controls the movements of muscles, though he might not be able to state what kind of animal it was taken from. The whole of the surface of the brain has been mapped out. In the brain we find centers for the motion of muscles, for feeling, sight, hearing, taste, smell, etc. In the lower kind of animals, the whole brain practically consists of these various centers. They make the brain. But as the brain gets bigger it is not the centres that get bigger, but they become gradually separated from one another by the growth of new parts of the brain between the old centres. The process goes on and on, until at last in mankind — and only in mankind — it has reached the stage at which vari¬ous special centers have become mere patches that lie here and there on the surface of man’s huge brain. These newer areas often called the silent areas play a very important part in the functioning of the brain. The nerve-fibres from them run in every direction. They run in definite groups and by definite ways to the other centers of the brain. They are the associate fibers. They associate one part of the brain with another.

If we compare the spinal cord of a dog with that of a man, there is not much difference between them. If we compare the cerebrum of a dog with that of a man, we find that the difference consists mainly in association of fibers and cells.

The grey mantle in the case of a man is much thicker. It is the greater number of association cells that makes it thicker. Generally, we may say that the difference between a high brain and a low brain is: that in the special centers the grey mantle is thicker in the high brain because there are a great many association cells in it, and that in the high brain the special centers are forced apart by the growth between them of new parts of the brain which bring all parts of the brain into connection with one another.

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