YOU are walking through the city street, thinking of nothing in particular, watching the passing throng, glancing idly about. But suddenly you stop short with your gaze riveted upon a shop window--something therein has caught your attention. Most of the time our minds drift. Tho there is a procession of images or ideas passing constantly across the field of consciousness, we give no heed to any one of them, but, like a leaf on the stream, float idly along. However, we have the power to single out one of these ideas and fix the whole mind upon it. And this is attention; it is holding one idea in consciousness to the exclusion of other ideas. For instance: A friend has made a remark which has hurt your feelings. If you fix your mind upon it--that is, think about it constantly--it gains a stronger hold upon your mind and you suffer correspondingly. Or, if you have a hole in your glove and fix your mind on it--keep thinking of it and looking at it--it will look bigger and bigger to you, until you think everybody you pass in the street is noticing it. And the . same is true of sensations. Suppose you have a pain. If you attend to it, think about it, and talk about it, it will grow worse, until after a while you will not be able to think or talk of anything We do not have to go far afield for the explanation; fear and imagination color the mental energy which the act of attention sends flying to the spot. Thus: Quotations from many eminent men might be adduced to enforce this point, but one from Dr. Carpenter must suffice: "The volitional direction of consciousness to a part suffices to call forth sensations in it, which seem to depend upon a change in its circulation; and if this state is kept automatically by the attraction of the attention, the change may become a source of modification not only in the functional action, but in the nutrition of the part." And if such a change is expected, as Dr. Braid suggests--that is, if the "expectant attention" is aroused--the result is much more marked. So if one is suffering from indigestion, and thinks he has eaten something indigestible, Let us see how it works out. In the chapter on the nervous system it was said that if the mental energy or vital force was depleted or unequally distributed the weakest spot would be the first to suffer. Now, suppose that your stomach is your weak spot. The nerves in the walls of your stomach (vasomotor) are unable to perform their functions because of an insufficient supply of force, consequently the circulation "lags superfluous"; there is not enough blood in the blood-vessels for This is no idle dream or vagary of fancy. It is based upon well-known laws of physiology and psychology, and repeated experiments have demonstrated its practicability. That such a use of attention changes the physical action of the partTHE ATTENTION