there is less disposition to calculous affections. So far, however, as we have had an opportunity for judging, it is secreted in greater quantity, and this may partly account for its seeming to have a smaller quantity of salts in any given amount; but the truth is, the freedom of the female from calculous affections is greatly owing to the shortness and size of the urethra, which admits the calculus to be discharged with comparative facility; and it is a common observation, that where the males of a family, hereditarily predisposed to gout, become, owing to their greater exposure to the exciting causes, affected with that disease, the females may be subject to calculous disorders, the two affections appearing to be, in some respects, congenerous. For the reasons already mentioned, however, stone rarely forms in the bladder of the female, and the operation of lithotomy is scarcely ever necessary. The desire to evacuate the contents of the bladder occurs more frequently in the female, probably, in part, owing to habit; and, in part, to the greater mobility of the nervous system.

In addition to these differences, as regards the secretions, the female has one peculiar to herself,—menstruation,—which has already engaged attention. In the progress of life, too, the glandular system undergoes evolutions which render it especially liable to disease. About the period of the cessation of the menses,—sooner or later, the mammæ frequently take upon themselves a diseased action, and become scirrhous and cancerous so as to require the organs to be extirpated.

In the treatment of disease, these sexual peculiarities have to be borne in mind. Owing to the greater mobility of the nervous system in the female, she usually requires a much smaller dose of any active medicine than the male; and, during the period when the sexual functions are particularly modified, as during menstruation, gestation, and the child-bed state, she becomes liable to various affections, some of which have been referred to elsewhere; others belong more appropriately to works on pathology or obstetrics.

The acquired differences, which we observe amongst individuals, are extremely numerous. The effect of climate on the physical and mental characteristics is strikingly exhibited. The temperate zone appears to be best adapted for the full development of man, and it is there that the greatest ornaments of mankind have flourished, and that science and art have bloomed in exuberance; whilst in the hot, enervating regions of the torrid zone, the physical and moral energy are prostrated; and the European or Anglo-American, who has entered them full of life and spirits, has left them after a few years residence, listless and shorn of his proudest characteristics. Nor is the hyperborean region more favourable to mental and corporeal development; the sensibility being obviously blunted by the rigours of the climate. The effect of locality is, perhaps, most signally exemplified in the Cretin, and the Goitreux of the Valais, and of the

countries at the base of lofty mountains in every part of the globe; as well as in the inhabitants of our low countries, who are constantly exposed to malarious exhalations, and bear the sallow imprint on the countenance. It has seemed to the author, that, in the Legislative Halls of Virginia, it has not been difficult to designate, by this means alone, the inhabitants of the upper and of the lower country.

Not less effective in modifying the character of individuals is the influence of the way of life, education, profession, government, &c. The difference between the cultivated and the uncultivated; between the humble mechanic, who works at the anvil or the lathe, and him whose avocation, like that of the lawyer and the physician, consists in a perpetual exercise of the organ of intellect; and between the debased subject of a tyrannical government, and the independent citizen of a free state,

"Lord of the lion heart and eagle eye,"

is signal and impressive.

To these acquired differences in individuals from extraneous or intrinsic causes we must refer habit, which has been defined,—an acquired disposition in the living body, become permanent, and as imperious as any of the primitive dispositions. It is a peculiar state or disposition of the mind, induced by the frequent repetition of the same act.

Custom and habit are frequently used synonymously: but they are distinct. Custom is the frequent repetition of the same act; habit is the effect of such repetition. By custom we dine at the same hour every day; the artificial appetite induced is the effect of

habit.

The functions of the frame are variously modified by this disposition, being at times greatly developed in energy and rapidity, at others largely diminished. If a function be over and over again exerted to the utmost extent of which it is capable, both as regards energy and activity, it becomes more and more easy of execution; the organ is daily better adapted for its production, and is so habituated to it, that it becomes a real want,—a second nature. It is in this way, that we accustom the organs of speech, locomotion, &c. to the exercise of their functions, until, ultimately, the most various combinations of the muscular movements of the tongue and limbs can be executed with surprising facility.

If, on the contrary, the organs of any function possess unusual aptitude for accomplishing it, and we accustom ourselves to a minor degree of the same, we ultimately lose a part of the aptitude, and the organs become less inclined, and less adapted to produce it. By custom, we may thus habituate ourselves to receive an unusually small quantity of nutriment into the stomach, so that at length it may become impracticable to digest more.

A similar effect occurs as regards the quantity of the special irri

tant, which we allow to impinge on any of the organs of sense. If we accustom them to be feebly impressed, yet sufficiently so for the performance of their functions, they become incapable of supporting a greater quantity of the special irritant without indicating suffering. The miner can see into the farthest depths of his excavations, when, to the eye of one who has descended from the bright light of day, all seems enveloped in obscurity. In this case, the sensibility of the organ of sight is developed, to such an extent, that if the individual be brought into even a feeble light, the impression is extremely painful. The nyctalope is precisely so situated. His nervous system of sight is so irritable, that, although he can see well in the night, he is incapable of accurate discrimination by day. On the other hand, exposure to intense light renders the sensibility of the visual nervous system so obtuse that objects are not so readily perceived in obscurity. The hemeralope, who sees in the day and not in the night, and who is consequently the anthiteton of the nyctalope, has the nervous system of vision unusually dull, and incapable of excitement by feeble impressions.

It may be laid down, as a general principle, that if we gradually augment the stimulus applied to any organ of sense, it becomes less susceptible of appreciating minor degrees of the same irritant; so that, in this way, an augmented dose of the irritant is progressively required to produce the same effect. This is daily exemplified by the use of tobacco,—either in the form of chewing, smoking, or snuffing, which becomes a confirmed habit, and can only be abandoned, without doing great violence to the feelings, by attention to the principle deduced from practice,—that by gradually following the opposite course to the one adopted in acquiring the habit,—that is, by accustoming the nerve of sense to a progressive diminution in the dose of the stimulus, an opposite habit may be formed, and the evil be in this manner removed.

When by habit we acquire extreme facility in executing any function, it may be executed apparently without the direct interference of volition. This is peculiarly applicable to the voluntary motions. We have elsewhere shown, however, that, in this case, habit only communicates the facility, and that there is no natural sequence of motions, and, consequently, no reason, as in executing a rapid musical movement, why one movement of the fingers should follow rather than another, unless volition were the guiding power. Volition, as Dr. Parr has remarked, is not an exertion of mind, but apparently a simple impulse directed almost necessarily to an end; and it is affected by custom, nearly like the organs of the body. Thus, a sensation, which excited a perceptible exertion of volition will, in time, produce it, and the correspondent action, without our being sensible of its interference; and so rapid is this progress, that we seem to will two ends or objects at the same time, though they are evidently, when examined, distinct operations. But though by custom we are no longer sensible of bodily impressions, or of the exer

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cise of volition, yet the corporeal organs in their several functions, acquire, like those of the mind, peculiar accuracy of discrimination. The musician is not, for instance, sensible of his willing any one motion; yet with the most exquisite nicety he touches a particular part of the string, and executes a variety of the nicest and most complicated movements with the most delicate precision.

It is a common remark, that "habit blunts the feeling but improves the judgment." To a certain extent this is true; but the feeling is not blunted unless the stimulant, which acts upon the organ of sense, be too powerful and too frequently repeated. When moderately exercised, the effect of education, in perfecting all the senses, is strongly exhibited, as we have elsewhere seen. Sensations, often repeated, cease to be noticed, not because they are not felt, but because they are not heeded; but if the attention be directed to the sensation, custom adds to the power discrimination. Hence the sailor is able to detect the first appearance of a sail in the distant horizon, when it cannot be perceived by the landsman; and the same kind of discrimination is attained by the due exercise of the other senses. This greater power of discrimination is doubtless owing to improvement in the cerebral or percipient part of the visual apparatus; but we have no evidence, that the organ of vision has its action necessarily blunted.

It has been presumed, by some physiologists and metaphysicians, that the will, by custom and exercise, may acquire a power over certain functions of the body that were not originally subject to it; nay, some speculatists have gone farther, and affirmed, that all the involuntary functions were originally voluntary, and that they have become involuntary by habit. Stahl and the other animists, who regarded the soul as the formative and organizing agent in animals, asserted, that it excites the constant movements of the heart, and of the respiratory, digestive and other nutritive organs, by habits so protracted and inveterate, and so naturalized within us, that these functions can be effected without the aid of the will, and without the slightest attention being paid to them. Respiration, according to them, is originally voluntary; but, by habit, the will becomes spontaneity; so that there is no farther occasion to invoke volition. Respiration goes on night and day, when we are asleep as well as awake; and they regard as a proof, that the action was originally dependent upon free will, that we are still able to accelerate or retard it at pleasure. They cite, moreover, the case of Colonel Townshend, related in another part of this work, to show, that the action of the heart is capable of being influenced by the will; and the fact that it is accelerated or retarded under the different passions.

CONDILLAC, LAMARCK* and DUTROCHET fantastically assert, that

The views of this distinguished naturalist regarding the effect of habit on organization, which he considers to tend to greater and greater complication, are most singular and fantastic. It is not, he considers, the organs of an animal that have given rise to its habits; on the contrary, its habits, mode of life, and those of its ancestors have, in the course of time, determined the shape of its body, the

the different instincts, observed to prevail so powerfully in animals, are mere products of an acquired power transmitted through successive generations.

The objections to all these views are,—that the functions in question are as well performed during the first day of existence as at an after period, and are apparently as free from the exercise of all volition. The heart, indeed, beats through fœtal existence for months before the new being is ushered into the world; and when, if volition be exerted at all, it can only be obscurely. The case of Colonel Townshend is strange, passing strange, but it is almost unique, and the power of suspending the heart's action was possessed by him a short time only prior to dissolution. All the functions in question must, indeed, be esteemed natural, and instinctive, inseparably allied to organization; and hence differing from the results of habit which is always acquired.

The opinion of Bichat, on the other hand, was, that habit influences only the animal functions and has no bearing on the organic or nutritive. But this is liable to objections. We have seen, under digestion, that if a bird, essentially carnivorous in its nature, be restricted to vegetable food, the whole digestive economy is modified, and it becomes habituated to the new diet. We know, also, that where drains are established in any part of the body, they become, in time, so much a part of the physiological condition of the frame, that they can only be checked with safety by degrees.

In the administration of medicines, habit has always to be attended to. The continued use of a medicine generally diminishes its power—hence the second dose of a cathartic ought to be larger than the first, if administered within a few days. Certain cathartics are found, however, to be exceptions to this. The Cheltenham waters are one. The constitution, so far from becoming reconciled to lead by habit, is rendered more and more sensible to its irritation. Emetics, too, frequently act more powerfully by repetition. Dr. Cullen asserts, that he knew a person so accustomed to excite vo

number and condition of its organs, and the faculties, which it enjoys. Thus the otter, the beaver, the waterfowl, the turtle, and the frog were not made webfooted that they might swim; but their parts having attracted them to the water in search of prey, they stretched out their toes to strike the water, and move rapidly along its surface. By the repeated stretching of their toes, the skin, which united them at the base, acquired a dabit or extension, antil, in the course of time, they became completely web-footed.

In like manner, the antelope was not endowed with a light, agile form, in order that it might escape by flight from the carnivorous animal; but by being exposed to the danger of being devoured by lions, tigers, and other beasts of prey, it was compelled to exert itself by running with great celerity; a habit, which, in the course of many generations, gave rise to the peculiar slenderness of its legs, and the agility and elegance of its form.

The cameleopard, again, was not gifted with a long flexible neck, because it was destined to live in the interior of Africa, where the soil was arid, and devoid of herbage; but, being reduced, by the nature of the country, to support itself on the foliage of lofty trees, it contracted a habit of stretching itself up to reach the high boughs, until its forelegs became longer than the hinder, and its neck so elongated that it could raise its head to the height of twenty feet above the ground!