diameter of a hair. When persons lie down to sleep, their thoughts take on the dream character before they can lose consciousness. "Look," says Sir Henry Holland, "to the passage from waking to sleeping, and see with what rapidity and facility these states often alternate with each other." Abstract reason gives place to images that begin to move at random before the mind's eye; if they are identified and considered, wakefulness continues. But at last they become vague, attention relaxes, and we sleep. It is possible to realize that one is sleeping, and to make an effort to awake and seize the mental train. But the would-be sleeper resumes the favorable position, the head drops, the senses lose their receptivity, and he who spent the last hour of the evening in revery in a darkened room has undergone but a very slight change when he passes into sleep. The images still run on while the body reposes, until, according to his temperament and habits, the brain becomes calm, and the soporific influence penetrates, we cannot tell how far, into the higher regions of the sensorium.
In considering the passing from the dream state into the waling state, several analogies are to be noted. Sometimes an amusing sense of the last dream occupies the attention deliciously for a few moments. Again, it is not uncommon to pass out of a dream into a perception of the hour of the night and of the situation, sink back into sleep, and take up the thread of the dream where it had been left at the moment of returning consciousness. More frequently the dream, if resumed, will be modified by physical conditions. At other times the painful consciousness of a frightful dream remains.
From these analogies the conclusion is reasonable that dreaming is a phenomenon of the mind, dependent upon changes in the circulation of the blood, and
