As a fog about a ship removes it from exact relations to surroundings, so, from the standpoint of morbid psychology, we may fancy the mind peering through a more or less misty envelope to the true adjustment to things--the "glass" through which we see "darkly." Were all action and reaction of the mind to surroundings perfectly adapted, there could be such a thing as _absolute_ sanity. So long, however, as evolution with continuous readaptation and the processes of dissolution with attempted adaptations continue, so long can there be but groping, imperfect relations to surroundings, so long must there be defective or morbid mental action, and sanity and insanity therefore but relative terms. Thus many symptoms of the insane appear to be but varying degrees of the morbid mental manifestations of health, and we may assume _a priori_ that they have a common genesis and can be identified for study. If we take, for example, one of the commonest of these--viz., the idea of persecution among the insane--we may safely identify it with the "sense of injury" equally common among the sane. By this "sense of injury" is meant that vague sense which afflicts many of us at times of being the object of hostile feelings on the part of others. No doubt we often _are_, for, in the stress of necessary rivalry and conflict upon which progress depends, we give and take injuries. But there remains a large excess of this "injured" feeling which can not be so explained, or which is disproportionate to its cause or entirely gratuitous, and is thus shifted into the field of morbid psychology. This only is here treated--the _morbid_ sense of injury. It seems to find an easy entrance to the mind from a mere feeling of being ill used or stinted in sympathy to the entertainment of serious grievances or persecutory ideas. In certain temperaments it is marked. On so-called "blue" days we are constantly moved to a "sense of injury" from fancied aloofness of our friends. Madam Lofty slights us, and our jaundiced imagination has it that she has heard something detrimental and dislikes us. But lo! to-day, when the liver is released, madam smiles sweetly, and never heard a thing.