In Cut No. 26 we are given an idea of a single nerve trunk in which are seen bundles of nerve fibres. Some of these nerve fibres are ascending; that is, afferent, or going towards the brain; and some are descending, that is, efferent, or going away from the brain.

In the picture of a cross section of a spinal cord, we have indicated how these different fibres are placed in a different locality, so that were we to cut a section of the cord with a knife, the resulting decay or degeneration of the nerve fibres would

differ. In those portions where the descending nerve fibres run the decay would be downwards, away from the brain; in those sections where the ascending fibres run the decay will be upwards, or towards the brain. So fibres can carry impressions only in their own direction, and, so far as we know, the nerve currents cannot be reversed. This bundling of fibres with the double insulation on the surface corresponds to the large subway pipes in which our telephone and telegraph wires are buried in New York City.

All along the spinal cord are little brains, portions of the nervous system presiding over special functions. Such, for example, are the centres devoted to breathing, to the action of the heart, to the acts of Nature.

We may have three different processes as a result of an im

pression from without: (1) The impression may come from along a nerve to the spinal cord, and unconsciously the expressions go out along another nerve fibre, resulting in an action. An

CUT No. 28. (Smith.)

example of this is the involuntary extension of the arm to break a fall. (2) An impression is received, acted upon by involuntary reflex, and then, after the action, telephoned to the brain, as shown by the diagram. The action proceeded from the spinal cord, but the knowledge of it went to the cerebrum. (3) An impression is received from without, telephoned through the spinal cord to the brain, under a deliberate fiat of the will, so that through the efferent nerves an expression results. We call these three kinds of actions Simple Reflex, Involuntary, and Voluntary.

The Localization of Functions in the Cerebrum.

This has been proved by study and experiments. There is a consensus of opinion that the thin gray rind of the cortex is definitely specialized. Two facts have been proved: the higher an animal stands in the grade of intelligence the more numerous are the folds and convolutions of the cortex (there are, however, a few exceptions to this rule); the cerebral functions have been definitely localized along certain portions of the cortex. There are sensory and motor nerves, that is, those that minister to sensation and those that minister to motion. Some of the efferent nerves are motor and some are not. Some of the motor nerves are voluntary and some are involuntary. Moreover each motor nerve is connected with some particular musele, not with the muscles in general, and precisely as the motor nerves are each

of them connected with some particular muscles, so they have their origin in different parts of the brain. (Fig. 29.)

CUT No. 29.

Association Fibres in the Cerebral Hemisphere.
(Shäfer after Meynert.)

Two diagrams of the localization of these motor functions are shown, the one showing the localization on the interior sur

face of the cerebrum, and the other along the median line as the

cortex dips down into the hemispheres.

Stream of Consciousness.

Professor James, the originator of the most striking example that we have to explain mental workings, likens them to successive sets or waves of feelings, of knowledge, of desires,

of deliberation constantly passing and repassing. On the surface of the stream float sticks and straws. Sometimes one idea is prominent, sometimes another. No one idea stands alone. The

thought is always complex. Sensations of our body, memories of distance, feelings, desires, all grow into one general thought of the moment. One can stand on the shore and fix the eye

upon a particular stick, as it floats along. That represents the thought in the Focus or Centre of attention.

So in the ever-flowing stream, the most striking thought is the brightest in the centre, while the others are grouped around it in the fading margin-other sticks, as it were, further down the stream. This Margin or Fringe, which is faint at first and hazy, is liable at any moment to be seized on by our attention and brought into the centre. Giving attention to any subject. is bringing it into the focus of our attention and holding it there.

Two great laws can be illustrated by this idea. (1) The thoughts that are present in this ever-flowing stream have been caused by the thoughts that have gone. This seems easy to understand. One can trace back, step by step, each thought from the present one, and see how each in turn has been caused by and is dependent upon its predecessor. (2) But the second law is harder to understand at first. It is, the thoughts that are coming have been influenced by the thoughts that are here. "What!" you may ask, "do you mean to say that thoughts yet unborn are influenced by the thoughts I am now thinking?" Yes, in a way, because it is not so much the single thought as a group of ideas. It is states of mind rather than an idea. Why is it that we can say, starting from the same word, "Our Father who art in Heaven," or "Father, whate'er of earthly bliss Thy sovereign will denies"? Why is not the word "Father" followed by the same sequence of words in every instance? It is like the constellation of the Great Dipper, where the stars are always in the same relation to each other, or like the mast of a ship, which is visible before the hull comes into view. So thoughts are below the threshold of consciousness with a small portion of the group of ideas appearing gradually into the consciousness. As Professor Adams puts it: "Other ideas, weak in themselves, owe their recall to the influence of their friends. The masses of ideas of which we have already spoken come into consciousness, or are driven from it, in a body. If for any reason one idea belonging to a mass finds its way into consciousness, it forthwith drags in a whole mass along with it. This is known as mediate recall, because certain ideas are recalled by means of, or through the mediation of other ideas. If in Sun