In short, there may exist not only a difference in the constitution of the different organs of the body, but these natural conditions are more or less changeful in their states, within certain limits, while still in a state of health. There may exist a condition of over-activity, or of under-activity, in any or all portions of the body, and from the operation of causes, the nature of which we are entirely ignorant, and concerning which persons do not much care, so long as they do not experience so much discomfort as to be unfitted for their usual occupations and pleasures. Such experiences are common with many persons, who yet remain in a condition of health. Passing now to the conditions of the mental side of the human system, we find, in what are called healthy states, that there exists as broad a diversity of character as in the physical. While some apprehend any thing a little abstruse with great difficulty, or fail to do so at all, others understand it with a readiness which we are accustomed to call intuition; while many occurrences seem merely to impinge upon and glance off the minds of some persons never to be remembered again, they pass from the minds of others only after long years, or remain through life. Some persons always look upon and judge of occurrences and results in an unusual way. They are odd or singular in their mental constitution, and are accustomed to do odd and out-of-the-way things just as naturally as others would do the same things in such a manner as to attract no attention. Some persons see, hear, taste, touch, and smell so much more quickly and delicately than others, that we must conclude there exists a radical difference in the perfection of the organization of the nerve-cells of these various organs of special sense. Again, there are periods in the experience of some persons, when they see, hear, touch, taste, and smell with much greater readiness and delicacy than at other times, even in a state of so-called health. Musical sounds are more delicate and pleasing; harsh and rough sounds are more harsh and rough; certain articles of food produce a keener sense of relish, and colors a greater sense of pleasure: all of which would indicate temporary changes in the structure or function of the nerve element comprising these special organs of sense.