sciousness is divisible into consciousness of self and consciousness of the relation of self to surroundings; and according as the one or the other region of the highest nervous arrangements is mainly affected, the disorder is mainly disorder of the consciousness of self, or disorder of the consciousness of the relation of self to surroundings.

In every case of insanity there are present all the three factors-disorder of the highest nerve arrangements, disorder of conduct, and disorder of consciousness; and in every case the disorder of consciousness includes disorder of thought and of feeling, of self-consciousness and of consciousness of the relation of self to surroundings. In no two cases, however, are these various factors combined in quite the same way, and thus no two cases precisely resemble one another. On the way in which they are combined depends the form which the insanity assumes.

CHAPTER V.

THE CAUSES OF INSANITY.

Heredity.

INSANITY is, in mathematical terms, a function of two variables. That is to say, there are two factors, and only two, in its causation; and these factors are complementary. Both enter into the causation of every case of insanity, and the stronger the influence of one factor, the less of the other factor is needed to produce the result. These two factors are, in brief, heredity and stress. It has been explained that, in order to work efficiently, the nervous system should have in a high degree a certain form of instability an instability which allows of ready and free rearrangement of the atoms of its molecules, with easy and copious liberation of the energy accumulated in them. So long as this rearrangement proceeds without actual decomposition of the molecule, the process remains within the limits of the normal; but it is easy to see that this form of instability has a certain relationship to another form-a form in which the disturbance of the molecules does not stop short at rearrangement, but goes on to partial or even to total decomposition. Since a certain degree of instability of the first form is an essential to nervous action, and necessarily exists in every possessor of a nervous system, and since this form of instability is related, more or less closely, to the second form, it is obvious that some tendency to the second form of instability exists in every

individual. The amount or strength of the tendency varies with each individual, but in every one it exists to some degree.

It is manifest that the amount of disturbance that is necessary to upset any orderly arrangement depends entirely on the stability of the arrangement. When the component parts of a structure are firmly compacted together, a violent disturbance will be necessary to upset or disintegrate the structure; and when the cohesion between the component parts is but feeble, the structure will be liable to disintegration from disturbances of a much less pronounced and less violent character. A jerry-built villa is liable to be blown down by a storm of wind, but nothing short of an earthquake will destroy a well-constructed mansion.

Now insanity is a disorder of the highest nervous centres; that is to say, a derangement of the structure of these centres, and this derangement of structure will be produced by slight disturbances where the structure is loosely compacted and the instability great; while in cases in which the structure is well and soundly constituted and of firm stability, it will require a violent disturbance to upset its equilibrium. Hence we find that, according to the opening statement, insanity is a function of two variables. It needs for its production a certain instability of nervetissue, and the incidence of a certain disturbance. When the instability of tissue is great, a small disturbance will suffice. When the instability is small, a violent disturbance is necessary. But for every individual, as for every wooden beam, there is a breaking-point. If you load a beam with sufficient weight, a certain weight will be found, varying with the strength of the beam, at which the beam will break; and if you subject a man to stress, a certain stress will be found, varying with the stability of his nervous system, at which the man will become insane. Hence, to determine the causes of insanity, we have to find, first the factors which tend to initial stability or instability of the highest nervous arrangements; and, second, the nature and

severity of the stresses to which these arrangements are subject.

The fact that the majority of people do not become, or do not remain, insane, indicates that they possess a nervous organization of sufficient stability to withstand such stresses as they are subject to. And the minority who become or remain insane, are endowed with a nervous organization which is either more easily upset, or is subject to stress of greater severity. As a matter of fact the factor which is chiefly and most often at fault is the nervous organization. Although, as has been said, there is an intensity of stress which will permanently upset even the most stably constituted nervous system, yet stresses of this extreme severity are so rare in human experience, that in practice a person of normal and average nervous constitution will not be driven mad by any of the ordinary vicissitudes of life. And since, in the vast majority of cases of insanity, we find that the occasion of the disorder was some stress of but medium intensity, we may be quite sure that in all such cases the important factor in the production of the insanity is not the magnitude of the disturbance, but the fragility of the arrangements on which the disturbance breaks.

The stability or instability of a person's highest nervous arrangements depends primarily and chiefly upon inheritance. Every man is the outcome and the product of his ancestry; and this is true not only of the broad and fundamental characters by which he is animal, by which he is human, by which he is national, by which he betrays the country and the family from which he proceeds; but extends to the trivial and minutely trivial characters by which he is distinguished from other individuals of his own race, country, and family. Doubtless every man is to some extent moulded into conformity with cirumstances by the influence of circumstances upon him; but the small amount of new character that circumstances can produce in any individual, in comparison with the characters transmitted to him by his ancestry, may be gathered from the length of

time that circumstances can act upon him, in comparison with the aggregate length of time during which the long line of his ancestry have been subject to modification by circumstances. Doubtless if we take a seedling plant, and if, while it is young, and its tissues plastic, and its potentialities undeveloped, we subject it to certain conditions of life, we can modify the arrangement and alter the stability of its most elaborate and highly-organized parts-of its flowers and fruit; and doubtless, also, if we subject a child to certain conditions of life, we may in the same way modify the arrangement and alter the stability of its most elaborate and most highly-organized parts-of its highest nervous centres; but the fact remains that, for the great majority of people, the question of the stability or instability of their highest nervous arrangements resolves itself into a question of the kind and degree of organization that they have inherited from their ancestry. To ascertain, then, the influence of the first factor in the production of insanity, it will be necessary to give a brief account of the laws of heredity.

The laws of heredity are two: the Law of Inheritance, and the Law of Sanguinity. Both of them are important in connection with the causation of insanity.

The Law of Inheritance is simple, and is easily stated and understood. It is that the offspring tend to inherit every attribute of the parents, or that every attribute of the parents tends to appear in the offspring, and will appear unless some counteracting influence prevents. Doubtless there are many cases in which attributes of the parents fail to appear in the offspring, but these are not exceptions to the law. The laws of nature know of no exception, and when apparent exceptions occur, it is either because the laws are acting in ways not understood, or because of the interference and counteraction of other laws. The rising of a balloon is not an exception to the law of gravity, it is an illustration of the law acting in an unusual way.