THE DOMAIN OF PHYSIOLOGY.

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Its present imperfection.

physics and physics; and the strife can be ended only by the decision of positive philosophy, as to what position shall be occupied by the study of living bodies. The present backwardness of the science is explained by the extreme complexity of its phenomena, and its recent date. That complexity forbids the hope that biological science can ever attain a perfection comparable to that of the more simple and general parts of natural philosophy: and, from its recent date, minds which see in every other province the folly of looking for first causes and modes of production of phenomena, still carry these notions into the study of living bodies. For more than a century intelligent students have in physics put aside the search after the mystery of weight, and have looked only for its laws; yet they reproach physiology with teaching us nothing of the nature of life, consciousness, and thought. It is easy to see how physiology may thus be supposed to be far more imperfect than it is; and if it be, from unavoidable circumstances, more backward than the other fundamental sciences, it yet includes some infinitely valuable conceptions, and its scientific character is far less inferior than is commonly supposed. We must first describe its domain.

Its field.

There is no doubt that the gradual development of human intelligence would, in course of time, lead us over from the theological and metaphysical state to the positive by a series of logical conceptions. But such an advance would be extremely slow; and we see, in fact, that the process is much quickened by a special stimulus of one sort or another. Our historical experience, which testifies to every great advance having been made in this way, shows that the most common auxiliary influence is the need of application of the science in question. Most philosophers have said that every science springs from a corresponding art;-a maxim which, amidst much exaggeration, contains solid truth, if we restrict it, as we ought. to the separation of each science from the theological and metaphysical philosophy which was the natural product of early human intelligence. In this view it is Relation to true that a double action has led to the inMedicine. stitution of science, the arts furnishing posi

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tive data, and then leading speculative researches in the direction of real and accessible questions. But there is another side to this view. When the science has once reached a certain degree of extension, the progress of speculative knowledge is checked by a too close connection of theory with practice. Our power of speculation, limited as it is, still far surpasses our capacity for action : so that it would be radically absurd to restrict the progress of the one to that of the other. The rational domains of science and art are, in general, perfectly distinct, though philosophically connected: in the one we learn to know, and therefore to foreknow; in the other to become capable, and therefore to act. If science springs from art, it can be matured only when it has left art behind. This is palpably true with regard to the sciences whose character is clearly recognized. Archimedes was, no doubt, deeply aware of it when he apologized to posterity for having for the moment applied his genius to practical inventions. In the case of mathematics and astronomy we have almost lost sight of this truth, from the remoteness of their formation; but, in the case of physics and of chemistry, at whose scientific birth we may almost be said to have been present, we can ourselves testify to their dependence on the arts at the outset, and to the rapidity of their progress after their separation from them. The first series of chemical facts were furnished by the labours of art; but the prodigious recent development of the science is certainly due, for the most part, to the speculative character that it has assumed.

These considerations are eminently applicable to physiology. No other science has been closely connected with a corresponding art, as biology has with medical art,—a fact accounted for by the high importance of the art and the complexity of the science. But for the growing needs of practical medicine, and the indications it affords about the chief vital phenomena, physiology would have probably stopped short at those academical dissertations, half literary, half metaphysical, studded with episodical adornments, which constituted what was called the science little more than a century ago. The time however has arrived when biology must, like the other sciences, make a fresh start in a purely speculative direction, free from all

RELATION OF PHYSIOLOGY TO MEDICINE.

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And when

entanglement with medical or any other art. this science and the others shall have attained an abstract completeness, then will arise the further duty, as I have indicated before, of connecting the system of the arts with that of the sciences by an intermediate order of rational conceptions. Meanwhile such an operation would be premature, because the system of the sciences is not completely formed; and, with regard to physiology especially, the first necessity is to separate it from medicine, in order to secure the originality of its scientific character, by constituting organic science as a consequence of inorganic. Since the time of Haller this process has gone on; but with extreme uncertainty and imperfection; so that even now the science is, with a few valuable exceptions, committed to physicians, who are rendered unfit for such a charge both by the eminent importance of their proper business, and by the profound imperfection of their existing education. Physiology is the only science which is not taken possession of by minds exclusively devoted to it. It has not even a regularly assigned place in the best-instituted scientific corporations. This state of things cannot last, the importance and difficulty of the science being considered. If we would not confide the study of astronomy to navigators, we shall not leave physiology to the leisure of physicians. Such an organization as this is a sufficient evidence of the prevalent confusion of ideas about physiological science; and when its pursuit has been duly provided for, that reaction for the benefit of art will ensue which should put to flight all the fears of the timid about the separation of theory from practice. We have seen before how the loftiest truths of science concur to put us in possession of an art; and the verification of this truth, which physics and chemistry have afforded before our eyes, will be repeated in the case of physiology when the science has advanced as far. Having provided for a speculative view of physiology, we must inquire into its object;

Its object.

and, as the vital laws constitute the essential subject of biology, we must begin by analysing the fundamental idea of life.

Before the time of Bichat, this idea was wrapped in a mist of metaphysical abstrac

Idea of Life.

tions; and Bichat himself, after having perceived that a definition of life could be founded on nothing else than a general view of phenomena proper to living bodies, so far fell under the influence of the old philosophy as to call life a struggle between dead nature and living nature. The irrationality of this conception consists especially in its suppressing one of the two elements whose concurrence is necessary to the general idea of life. This idea supposes. not only a being so organized as to admit of the vital state, but such an arrangement of external influences as will also admit of it. The harmony between the living being and the corresponding medium (as I shall call its environment) evidently characterizes the fundamental condition of life; whereas, on Bichat's supposition, the whole environment of living beings tends to destroy them. If certain perturbations of the medium occasionally destroy life, its influence is, on the whole, preservative; and the causes of injury and death proceed at least as often from necessary and spontaneous modifications of the organism as from external influences. Moreover, one of the main distinctions between the organic and the inorganic regions is that inorganic phenomena, from their greater simplicity and generality, are produced under almost any external influences which admit of their existence at all; while organic bodies are, from their complexity, and the variety of actions always preceding, very closely dependent on the influences around them. And the higher we ascend in the ranks of organic bodies, the closer is this dependence, in proportion to the diversity of functions; though, as we must bear in mind, the power of the organism in modifying the influences of the medium rises in proportion. The existence of the being then requires a more complex aggregate of exterior circumstances; but it is compatible with wider limits of variation in each influence taken by itself. In the lowest rank of the organic hierarchy, for instance, we find vegetables and fixed animals which have no effect on the medium in which they exist, and which would therefore perish by the slightest changes in it, but for the very small number of distinct exterior actions required by their life. At the other extremity we find Man, who can live only by the concurrence of the most complex exterior conditions, atmospherical and

DEFINITION OF LIFE.

terrestrial, under various physical and chemical aspects; but, by an indispensable compensation, he can endure, in all these conditions, much wider differences than inferior organisms could support, because he has a superior power of reacting on the surrounding system. However great this power, it is as contradictory to Bichat's view as his dependence on the exterior world. But this notion of Man's independence of exterior nature, and antagonism to it, was natural in Bichat's case, when physiological considerations bore no relation to any hierarchy of organisms, and when Man was studied as an isolated existence. However, the radical vice of such a starting-point for such a study could not but impair the whole system of Bichat's physiological conceptions; and we shall see how seriously the effects have made themselves felt.

Next ensued the abuse, by philosophers, and especially in Germany, of the benefits disclosed by comparative anatomy. They generalized extravagantly the abstract notion of life yielded by the study of the aggregate of organized beings, making the idea of life exactly equivalent to that of spontaneous activity. As all natural bodies. are active, in some manner and degree, no distinct notion could be attached to the term; and this abuse must evidently lead us back to the ancient confusion, which arose from attributing life to all bodies. The inconvenience of having two terms to indicate a single general idea should teach us that, to prevent scientific questions from degenerating into a contest of words, we must carefully restrict the term life to the only really living beings, -that is, those which are organized, and not give it a meaning which would include all possible organisms, and all their modes of vitality. In this case, as in all primitive questions, the philosophers would have done wisely to respect the rough but judicious indications of popular good sense, which will ever be the true starting-point of all wise scientific speculation.

I know of no other successful attempt to define life than that of M. de Blainville, definition. De Blainville's proposed in the introduction to his treatise

on Comparative Anatomy. He characterizes life as the double interior motion, general and continuous, of com