are carried on by these properties acting through the medium of organization.* The same properties are rendered more transiently mutable to carry out the act of gestation and lactation in animals, and fructification in plants. In the former cases, the changes are abundantly manifest; and then the powers of all other parts must be so constituted as to adapt themselves to those transient modifications through which gestation and lactation are accomplished. And since, therefore, the organic properties are rendered mutable for those great natural ends, and susceptible of various influences for the purposes of life, they are unavoidably but contingently liable to changes of a morbid nature when certain unnatural causes may happen to exert their effects upon them, and those morbid changes are even analogous to those of gestation and lactation. So, also, for the same reason, when other causes operate, they are liable to other artificial changes; and it is found from observation that, among these latter causes, there are many that will produce such changes as will enable the morbid properties to take on their natural tendency towards a state of health. If, there

* See Institutes of Medicine, (Age and Sex,) p. 373–383, p. 393.

fore, it be miasma which operates upon them, fever may ensue, and then, perhaps, a cathartic, or an emetic, by a different impression, will place nature in the way of passing again to her ordinary state. All the changes, too, which constitute the different forms of disease, are attended by such modifications of irritability and sensibility, that the subjects of such changes are very differently affected by physical agents than in the condition of health.* All this, too, will be according to the combined circumstances which make up the nature of the change; and it is the finding out of these circumstances in every case of disease, and at all stages of its progress, and adapting our means of cure in conformity with them, which form the greatest difficulties in practical medicine.

Now, gentlemen, this mutability of the properties of life is at the very foundation of the healing art. When they are driven from their natural standard to a morbid state, it is more or less their tendency to return to their healthy condition. This tendency may be often greatly pro moted by art; but in many instances, as in the selflimited diseases, it so far transcends all artificial

*See Author's Institutes, &c., § 137-160.

impressions, that, in a general sense, it will admit of little or no interference. This great law, therefore, is at the very basis of medicine. Without it, remedial agents would be powerless; the knife of the surgeon, and his caustics and poultices, would have had no existence. It is the sole dependence of plants and of the brute creation. All animated nature, indeed, would utterly perish without it. Galen in one line expresses beautifully the whole extent of the doctrine. "Natura malum sentiens gestitat magnopere mederi." Nature cast down desires greatly to be assisted.

The general tendency, of which I have now spoken, in the properties of life to return from their morbid to their natural state, whether spontaneously or brought about by art, has been long known as the Vis Medicatrix Nature-the recuperative power of Nature. It is a great organic provision, which is often through misapprehension, and not seldom ironically, represented as a principle of intelligence; while it is nothing more than a natural law impressed upon the constitution of all organic nature. Hence it is that all right-thinking physicians have regarded and designated Medicine as the "Handmaid of Nature." You perceive, therefore, gentlemen, that

this also is a very good name, so only you agree to understand alike its proper import. None understood it better, or has expressed it better, than the father of Medicine. "Natura deficiente," he says, "quicquam obtinet medica ars, perit æger." If Nature come not to the aid of the medical art, the sick man dies. And Celsus to the same effect: "Natura repugnante, nihil proficit medicina." If Nature do not co-operate, medicine is useless. Or, as the poet has it,

*

"When Nature cannot work, th' effect of art is void."

*It is from the want of a proper understanding of the recuperative efforts of Nature under circumstances of disease, and too often from no understanding of the subject, that so many physicians rely altogether upon art for the cure of diseases; while, in truth, art can only place the morbid states in the way of curing themselves. Nature does all the rest; and therefore it is that the best practice often consists in doing nothing more than keeping all obstacles out of the way of Nature. All this is conspicuously seen in diseases that have a certain allotted course and duration, as smallpox, measles, scarlet fever, mumps, &c. This principle, indeed, is at the foundation of the success of homœopathy and animal magnetism, more or less aided by confidence and hope. The work of cure, in this popular practice, is left to the spontaneous efforts of Nature, while the mind is agreeably entertained and encouraged by the powerless and inoffensive doses that are administered under the disguise of remedies, or by an appeal alone to the imagination.

Were it not, therefore, for the natural tendency implanted in the constitution of the properties of life to return from morbid to

I have said that physiology is so completely at the foundation of all the changes which befall the living being, that the same great principle

their natural states, there could never be a recovery from disease. But something more than this natural recuperative tendency is necessary in grave diseases. There must be either help from art or other help from Nature. But it is only a small proportion of mankind, and but few of the brute creation, that can have the be nefit of art; and, from the fallacies of human judgment, art itself is often imbecile. Nature has therefore instituted a great variety of processes for her own protection and preservation, though they all depend upon a few simple laws, or, more comprehensively, what I have denominated the law of adaptation. We see the principle first exhibited in the various permanent provisions for self-defence, such as thorns, horns, the galvanism of certain animals, the poison of serpents, of insects, &c. (See page 103) The most obvious step in the chain of analogies is the variety of provisions for perpetuating the species; such as relate to animal and vegetable reproduction, the wings and burrs of seeds for their dispersion, &c. Then comes another class for the preservation of every individual; such as the various contrivances for procuring food, &c.; and here, too, should be included the food itself, the air, &c. Now, with all these provisions for the maintenance of life in a state of health, it would be absurd to suppose that a fundamental principle has not been implanted in the properties of life for their direct preservation, when they may become deranged by various That this is so, is a matter of constant observation; and this observation of the spontaneous subsidence of disease, or as the most violent poisons of the materia medica may contribute to its removal by establishing changes that are more favorable to the recuperative process than such as are brought about by the ordinary causes of disease, enforce still more the conviction that it would have been the greatest possible defect in the general plan

causes.