power is thus rendered an agent by which all parts are balanced in their healthy functions, by which all parts are rendered sensitive to the condition of each other, and by which, when one becomes disturbed, another, or all other parts, may be thrown into disordered action. In the natural state, for example, if the skin be chilled and perspiration checked, the nervous power immediately excites the kidneys to an increased secretion of urine. Another plain example of an analogous process occurs in every act of respiration, and the process of respiration exemplifies exactly what is or should be meant by sympathy. The mind and its passions are also constantly bringing the nervous power into an endless variety of influences, both in organic and animal life. In the former case, we see its operation directed upon the stomach when vomiting is brought on by the imagination, and upon the capillary blood-vessels of the face, when shame or anger suffuses the countenance. There is nothing like all this in plants.*

We have thus a great symmetrical system, in structure, properties, functions and organic re

* Ibid, § 222-233, 500, which embraces a summary view of the doctrine which I have propounded of the functions of the nervous power.

sults, which is alike common to all animated nature, while certain additions are provided in animals to answer some special ends of their being.* You all see that it is a consistent, a harmonious plan, and that it is only when we depart from the obvious path of nature, that incongruities begin to appear. I say you are already convinced that truth in physiology is just as simple and as easily comprehended as it is everywhere else. To beget conviction, it is only necessary

* Much confusion has prevailed upon this subject, in consequence of too great a distinction which had been drawn by Bichat between the life which is common to plants and animals, and which is known as organic life, and the superaddition of certain organs and functions to animals, and which is called animal life. Bichat conveys the impression of two distinct lives, as appertaining to animals, while, in point of fact, what is peculiar in their life is engrafted upon organic life. There is but one principle of life; but in animals, besides what is common to it with the vegetable tribes, it possesses certain other endowments that do not manifest themselves in plants. For the sake of brevity and convenience, however, we may speak of organic and animal life; but, in having so done, I wish to be understood that I recognise but one life, though modified even in its purely organic aspect in the two departments of living Nature. (See Institutes of Medicine, § 183-185.)

In the work to which reference is here made, I have endeavored to analyse the whole of this subject, and to bring it out of the confusion in which it had been involved, and redeem it from the metaphysical mystery with which it had been charged by the physical theorists.

to present it in its naked simplicity, and it will then be self-evident to any mind that has not entangled itself in the prejudices of error. Hence, too, you will readily appreciate the importance of beginning right, and with a determination to reject whatever conflicts with the self-evident propositions of truth. Whatever infringes upon the consistency and the unity of the great plan of organic nature, you may depend upon it, is the spurious work of man. I do not mean, however, that you should turn your sight from error as it dances before you; for whatever is dignified in truth will always gain by any just comparison; and you should know the false that you may assist in restraining its progress.

Such, you see, gentlemen, is my solicitude for your safety, that I have again wandered from my subject to show you the importance of not departing from it yourselves. But I can only now present you the great landmarks which should guide your steps throughout all that domain of nature which it is our province to cultivate. Nor have I done more than make a general survey of animated existence as presented in its most natural aspects. Looking at this alone, we should imagine that it is all without change, and that every living being is destined to live on for ever.

There is nothing in the perfect state of animals or plants which denotes their mutability beyond what is incident to growth and nutrition-nothing of the liability of all to disease, or death. All this is inferred from another series of observations; and here we pass into the vast fields of pathology and therapeutics. But there is no possibility of entering those regions but by the great domain of physiology. It is true, shorter cuts have been often attempted, and in recent times it would seem almost as if they had been overrun by foes and plundered of all that is valuable, or which entitles them to our respect or attention. Your help is wanted in maintaining the integrity of nature; in repairing the breaches that have been made in the bulwarks which she has erected. You will find much in the artificial systems of physiology that is so estranged from nature that you will have no chance of smiling even at a clumsy caricature; and when you turn to pathology and therapeutics, as managed by the same philosophers, you will be amazed to see how these three branches of science have been stripped of their relations to nature. Should you, however, be inclined to follow those inquirers who have been guided by the light of truth, you will find all my assurances sustained by your own ob

servations. You will find nothing inconsistent in any branch of your pursuits, and that the whole is bound together by the closest affinities. You will find that physiology, in its connection with organization, lies at the foundation of pathology and therapeutics, and of all those intermediate changes which make up the transient or permanent differences among individuals of the same species. All the changes that may befall the most natural state of the being, from the most aggravated forms of disease to temperament itself, are intrinsically nothing more than the physiological states more or less turned from their natural standard; while therapeutics is only the method of turning them back again. For great and wise purposes, the properties of life are rendered mutable, and as one cause or another, and according to its virtues, may make its impressions upon irritability or sensibility, so will it be felt, and corresponding effects will follow. The progress of structural development from the beginning, of life, especially such as marks the different eras, both in animals and plants, as, for example, from the embryo and seed to the evolution of the structure, and again remarkably at the age of puberty, is partly due to modifications which the organic properties undergo; since all the processes of life