more people of great genius, at one time or other of their lives, exhibit manifestations of insanity than do persons of ordinary mental faculties. And it is not to be doubted that the genius which prompts to exaltation in literature and the fine arts is more apt to be associated with or to end in insanity than that which leads to superiority in any one or more of the sciences. In literature and art the imagination is strained to the utmost if the highest standard of originality and excellence is to be attained, and the imagination is assuredly that faculty of the intellect which is least tolerant of straining. The genius, on the contrary, which is concerned with mathematics, astronomy, or any one of the sciences or mechanical arts, deals with facts instead of fancies; and there is nothing about facts and their study which in the least predisposes to mental derangement. The great biologists and chemists, for instance, who have become insane, are so few in number that I cannot at this moment recall a single one; while among great poets, painters, novelists, and musicians, who have either with their genius shown symptoms of insanity, or who toward the close of life passed into fatuity, the names of Tasso, Burns, Swift, Mozart, Hayden, Walter Scott, Blake, and Poe at once come to mind.

The practical lesson to be derived from all this is, that care should be taken that young persons who evince more than ordinary talent for any particular branch of literature, science, or art, should be encouraged to exercise their minds to some extent in other directions. The concentration of the intellect upon a single subject, while yet the individual has scarcely learned how to use his mind, can only be regarded as deplorable.

CHAPTER VII.

HABIT.

WHEN a living being performs an act under the operation of certain impressions which are received, there is a tendency toward the performance of a similar act, if like influences are brought to bear upon the organism. Every time the act is performed, the disposition to repeat it becomes stronger, until at last the tendency is so firmly established that the act is

accomplished without the reception of impressions of like character to those which originally gave rise to it, but solely through the force of the newly acquired power. If from any cause the act is impossible of performance, the impulse still exists, and produces more or less unpleasant feeling in the mind, or sensation in the part of the body with which it is in relation.

This disposition to repetition is not limited to physical acts; it prevails in regard to almost every function of the body and mind, and forms often an important element in the production of disease.

Habit, therefore, is periodicity, and may be defined as the disposition which the organism acquires from the frequent reception of certain impressions, the indulgence in certain modes of thought, or the performance of certain acts, to continue in the accustomed course till some more powerful force intervenes.

A person, therefore, who has dined for many years regularly at the same hour, experiences the sensation of hunger when the time for eating arrives; the orator or writer who has long been in the habit of arranging his thoughts in a particular way, or of making use of peculiar modes of expression, follows the familiar methods with such unfailing regularity that, if he has spoken or written much, his style is at once recognized by those who have given it their attention; and the workman, who for years has observed a certain order or sequence in the performance of his duties, continues the system unchanged throughout his whole life.

But all these and other like habits may be broken up. The person who has dined habitually at six o'clock is taken ill, and, attributing his sickness to the fact of eating late in the day, changes his dinner-hour to one nearer noon. The orator or writer, finding that his speeches or essays are not so well received by the public as he would wish, alters his line of thought and characteristic phraseology to others which he thinks will be more effective; and the workman, losing his position, obtains employment in another shop where a change in his methods becomes necessary. Such changes are, however, not accomplished without considerable trouble, and sometimes with great suffering.

An instance cited by Dr. Carpenter' will recall many similar ones to the reader.

1.66

"Principles of Mental Physiology," etc., London, 1874, p. 354.

"The first child of a young mother was accustomed, before being put into his cradle for his mid-day sleep, to be 'hushed off' in the arms of his mother or his nurse. But, having been told that this was an undesirable practice, his mother, wishing to break him of the habit, one day laid him down awake in his cradle and remained behind the head of it, so as to be out of the infant's sight. He screamed so long and so violently that several times she almost relented, fearing that he would injure himself; but she had firmness to persevere, and, after a while, the child cried himself to sleep. Next day the screaming fit was much shorter, and on the following day shorter still; and in a few days the child ceased to cry when laid down, and never did so again."

It is a well-known fact that the impressions or consequences which result from the action of certain agents are less marked as the operation of the cause is repeated. Thus, the system becomes habituated to the action of alcohol, opium, and many other substances, so that while a small quantity will, in the first instance, produce the characteristic result, the dose must be larger each time that it is taken, or be more frequently repeated, in order that a corresponding effect shall be produced.

There are many noxious agents to the action of which the system may become so habituated by frequent repetition or the continuation of their action that no injurious results follow, when, without the protection thus afforded, disease, or even death, would be produced. Persons living in a malarious district, and who are thereby constantly exposed to the deleterious emanations of the locality, are often, in time, so hardened to the influence that it fails to cause its ordinary effects, while, as regards those newly arriving in the region, its power to do harm remains unabated. Acclimation is nothing but the acquisition of immunity from disease by habitual exposure to the morbific elements of some particular place.

In like manner, a perception, an emotion, or a thought, which, when first experienced, caused a good deal of mental and physical disturbance, by repetition loses little by little the energy it once possessed, and scarcely excites a ripple in the usually placid mind or body of the individual.

The influence of habit over the ordinary operations of the economy is constantly seen; the sensations of hunger and thirst are experienced at stated periods of the day, because,

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by frequently eating or drinking at those times, the system, as it were, expects a repetition, and hence the regular recurrence of the feelings in question. The action of the same law is seen in the periodical return of the desire to evacuate the bowels at the same hour, when by habit we have become accustomed to the act at that time. So with the desire for sleep, the hour of awaking, and the inexpressible sensations excited by the want of the usual cigar or alcoholic stimulant, with many others which must be familiar to every reader.

The manners and customs of nations are mainly the result of habit, continued through a long succession of generations. It is as difficult to alter them as it is to change a long-established habit of the individual organism.

Some persons are more under the influence of habit than others; they acquire a habit more quickly, and lose it with less facility. So strong are the unpleasant feelings excited by any interruption in the regular course of their habits that they will endure the greatest inconveniences to indulge them. I knew a gentleman whose custom it was to touch a certain tree-on the road from his house to the railway station, a distance of about five miles-as he daily went to his place of business. On one occasion, through absence of mind, he neglected this action, and rode several hundred yards before he discovered his omission. Though feeling annoyed, he continued his journey; but the uncomfortable sensation became too strong for him to endure it any longer, and, after having ridden nearly two miles past the tree, he galloped back, at the risk of missing the train, and touched it as usual.

Many persons, as is well known, have great difficulty in getting to sleep in any other bed than that to which they have become accustomed. No matter how luxurious the bed may be, sleep is effectually banished, often for several hours, and sometimes for the whole night.

In explanation of the essential cause of habit we can bring forward nothing very definite. We know that with inorganic matter a force once acquired will continue indefinitely, if no more powerful force interferes with it. A ball thrown into the air would continue in motion but for the influence exerted by gravity and friction. We can conceive of a similar law being in operation on organized matter. An impression is made upon the brain, and through the nervous system certain thoughts or actions ensue. The impression is not effaced with

the accomplishment of the resultant act; something of it remains to be strengthened, perhaps, by a similar impression made the following day, at the same time, with similar results. The process is in some respects like the registering of impressions to constitute memory, differing mainly in the fact that there is no consciousness of the process, and that there is no voluntary effort made to recall the impressions. This course may continue from day to day until the associated thoughts or actions are produced without the original stimulus, and thus the habit is established.

For instance, a person is induced to smoke a cigar after dinner. The inducement, whatever it may be, constitutes the impression made upon the brain. The persuasion of a friend, the desire to be sociable, or the idea that smoking would be beneficial to the health, prompts to the performance of the act, and the cigar is smoked. It is repeated for the same cause until at last the act of repetition begins to exercise its effect, and the original incentive is lost sight of in the more powerful one which has taken its place. A want has been created. A habit has been fully formed, and it cannot be broken without violence both to mind and body. The oft-repeated impression has left its traces somewhere each time, until at last it assumes a local habitation and becomes permanently fixed in the organism, not to be lost except through some more powerful influence acting in a similar manner to the first.

I have known several instances in which choreic affections have been acquired through a habit of imitating those who were thus disordered in their nervous systems. In one of these a boy mimicked the involuntary facial contortions from which a schoolmate suffered. He kept up the actions at intervals during the morning, and then discovered, to his great dismay, that he had lost the power of control over them, having, in fact, become himself the subject of facial spasms exactly like those of his prototype. Here the original excitation of the will, acting upon a peculiarly sensitive system of motorcells, impressed them so strongly that, after a few repetitions of the volitional impulse, they were endowed with the power of carrying on the resultant movements through the force evolved by their own action. Several old ladies of strongly benevolent dispositions regarded it as resulting from a special dispensation of Providence.

Stammering, which is a chorea of the muscles of speech, is