There is no more interesting subject of inquiry open just now than that of the interaction between the thoughts of the mind and the configuration of the brain. The fair conclusion appears to be that each is greatly the cause of the other; that the character of the persistent thoughts actually shapes the cerebrum, while on the configuration of this organ depends in turn the manner of thoughts we think. Now, thought is, for the most part, automatic. We think, without intention or effort, as we have been accustomed to think, just as we walk or write without any conscious arrangement of muscles. Mozart could write an overture, laughing all the time at the little jokes his wife made to keep him awake; to be sure he had thought it out before, and there it was, ready to be written; but he did not consciously try for these musical thoughts, they simply came to him in proper succession. Coleridge thought “Kubla Khan” in his sleep, and wrote it when he awoke; and, indeed, he might as well have been asleep all the time for all he had to do with the production of most of his thoughts. “Over the buttons she falls asleep, And stitches them on in a dream,”-- is very possible and likely. For one thing which we consciously set ourselves to think about, a thousand words and acts come from us every day of their own accord; we don’t think of them at all. But all the same, only a poet or a musician could thus give forth poetry or music, and it is the words and acts which come from us without _conscious_ thought which afford the true measure of what we are. Perhaps this is why such serious weight is attached to our every “idle word”--words spoken without intention or volition. We are getting, by degrees, to Henry and his bad habits. Somehow or other, the nervous tissue of the cerebrum “grows to” the thoughts that are allowed free course in the mind. _How_, Science hardly ventures to guess as yet; but, for the sake of illustration, let us imagine that certain thoughts of the mind run to and fro in the nervous substance of the cerebrum until they have made a way there: busy traffic in the same order of thoughts will always be kept up, for there is the easy way for them to run in. Now, take the child with an inherited tendency to a resentful temper: he has begun to think resentful thoughts: finds them easy and gratifying; he goes on; evermore the ugly traffic becomes more easy and natural, and resentfulness is rapidly becoming _himself_, that trait in his character which people couple with his name.