where that eminent Scotchman had found the premisses of his argument.200 Both of these great inquirers arrived at truth, but each accomplished his journey by a different path. And this antithesis is accurately expressed by one of the most celebrated of living chemists, who, in his remarks on the composition of water, truly says, that while Cavendish established the facts, Watt established the idea.2 201

Thus much, as to what was effected by the Scotch in the department of inorganic science. If we now turn to organic science, we shall find that, there also, their labours were very remarkable. To those who are capable of a certain elevation and compass of thought, it will appear, in the highest degree, probable, that, between the organic and inorganic world, there is no real difference. That they are separated, as is commonly asserted, by a sharp line of demarcation, which indicates where one abruptly ends, and the other abruptly begins, seems to be a supposition altogether untenable. Nature does not pause, and break off in this fitful and irregular manner. In her works, there is neither gap nor chasm. To a really scientific mind, the material world presents one vast and uninterrupted series, gradually rising from the lowest to the highest forms, but never stopping. In one part of that series, we find a particular structure, which, so far as our observations have yet extended, we, in

200 "He" (i. e. Cavendish) "here omits entirely the consideration of latent heat; an omission which he even attempts to justify, in one of the passages interpolated by Blagden. But it is well known to every one acquainted with the first principles of chemical science, even as it was taught in the days of Black, and it was indisputably familiar to Mr. Watt, that no aeriform fluid can be converted into a liquid, nor any liquid into a solid, without the evolution of heat, previously latent. This essential part of the process, Mr. Cavendish's theory does not embrace; but without it, no theory on the subject can be complete; and it will presently be seen, that Mr. Watt took it fully into account." Muirhead's Life of Watt, p. 315.

201 Cavendish and Watt both discovered the composition of water. Cavendish established the facts; Watt the idea." "The attaching too high a value to the mere facts, is often a sign of a want of ideas." Liebig's Letters on Chemistry, London, 1851, p. 48. The last sentence of this illustrious philosopher, which I have put in italics, should be well pondered in England. If I had my way, it should be engraved in letters of gold over the portals of the Royal Society and of the Royal Institution.

VOL. II.

M M

another part, cannot find. We also observe particular functions, which correspond to the structure, and, as we believe, result from it. This is all we know. Yet, from these scanty facts, we, who, at present, are still in the infancy of knowledge, and have but skimmed the surface of things, are expected to infer, that there must be a point, in the chain of existence, where both structure and function suddenly cease, and, after which, we may vainly search for signs of life. It would be difficult to conceive a conclusion more repugnant to the whole march and analogy of modern thought. In every department, the speculations of the greatest thinkers are constantly tending to coördinate all phenomena, and to regard them as different, indeed, in degree, but by no means as different in kind. Formerly, men were content to ground their conviction of this difference in kind, on the evidence of the eye, which, on a cursory inspection, saw an organization in some bodies, and not in others. From the organization, they inferred the life, and supposed that plants, for instance, had life, but that minerals had none. This sort of argument was long deemed satisfactory; but, in the course of time, it broke down; more evidence was required, and, since the middle of the seventeenth century, it has been universally admitted, that the eye, by itself, is an untrustworthy witness, and that we must employ the microscope, instead of relying on the unaided testimony of our own puny and precarious senses. But the microscope is steadily improving, and we cannot tell what limits there are to its capacity for improvement. Consequently, we cannot tell what fresh secrets it may disclose. Neither can we say, that it may not be altogether superseded by some new artificial resource, which shall furnish us with evidence, as superior to any yet supplied, as our present evidence is superior to that of the naked eye. Even already, and notwithstanding the shortness of time during which the microscope has been a really effective instrument, it has revealed to us organizations, the existence of which no one had previ

ously suspected. It has proved, that what, for thousands of years, had been deemed mere specks of inert matter, are, in truth, animals possessing most of the functions which we possess, reproducing their species in regular and orderly succession, and endowed with a nervous system, which shows that they must be susceptible of pain and enjoyment. It has detected life hidden in the glaciers of Switzerland; it has found it embedded in the polar ice, and, if it can flourish there, it is hard to say from what quarter it can be shut out. So unwilling, however, are most men to relinquish old notions, that the resources of chemistry have been called in, to ascertain the supposed difference between organic and inorganic matter; it being asserted, that, in the organic world, there is a greater complexity of molecular combination, than in the inorganic.202 Chemists further assert, that, in organic nature, there is a predominance of carbon, and, in inorganic, a predominance of silicon.203 But chemical analysis, like microscopic observation, is making such rapid strides, that each generation, I had almost said each year, is unsettling some of the conclusions previously established; so that, now, and for a long time hence, we must regard those conclusions as empirical, and, indeed, as merely tentative. Surely a permanent and universal inference cannot be drawn from shifting and precarious facts, which are admitted to-day, and may be overthrown to-morrow. It would, therefore, appear that, in favour of the opinion, that some bodies are living, and that others are dead, we have nothing,

202 Organic substances, whether directly derived from the vegetable or animal kingdom, or produced by the subsequent modification of bodies which thus originate, are remarkable as a class for a degree of complexity of constitution far exceeding that observed in any of the compounds yet described." Fownes' Chemistry, 3d edit., London, 1850, p. 353. I quote this, as the first authority at hand, for a doctrine which is universally admitted by chemists, and which is indubitably true, so far as our experiments have at present extended.

203 "As the organic world is characterized by the predominance, in quantity, of carbon, so the mineral or inorganic world is marked by a similar predominance of silicon." Turner's Chemistry, edited by Liebig and Gregory, vol. ii. p. 678, London, 1847.

except the circumstance, that our researches, so far as they have yet gone, have shown that cellular structure, growth, and reproduction, are not the invariable properties of matter, but are excluded from a large part of the visible world, which, on that account, we call inanimate. This is the whole of the argument on that side of the question. On the other side, we have the fact, that our sight, and the artificial instruments, by whose aid we have arrived at this conclusion, are confessedly imperfect; and we have the further fact, that, imperfect as they are, they have proved, that the organic kingdom is infinitely more extensive than the boldest dreamer had ever imagined, while they have not been able to enlarge the boundaries of the inorganic kingdom to any thing like the same amount. This shows, that, so far as our opinions are concerned, the balance is steadily inclining in one given direction; in other words, as our knowledge advances, a belief in the organic is encroaching upon a belief in the inorganic.204 When we, moreover, add, that all science is manifestly converging towards one simple and general theory, which shall cover the whole range of material phenomena, and that, at each successive step, some irregularities are explained away, and some inequalities are reduced, it can hardly be doubted, that such a movement tends to weaken those old distinctions, the reality of which has been too hastily assumed; and that, in their place, we must, sooner or later, substitute the more comprehensive view, that life is a property of all matter, and that the classification of bodies into animate and inanimate, or into organic and

204 I mean, of course, to apply this remark only to the globe we inhabit, and not to extra-terrestrial phenomena. Respecting the organization or non-organization of what exists out of this earth, we have no evidence, and can hardly expect to have any for centuries. Inferences have, indeed, been drawn from telescopic observations; and attempts are now being made, abroad, to determine, by a still more refined process, the physical composition of some of the heavenly bodies. But without venturing, in this note, to enter into such discussions, or even to state their purport, I may say, that the difficulty of verification will long prove an insuperable barrier to our knowledge of the truth or falsehood of any results which may be obtained.

inorganic, is merely a provisional arrangement, convenient, perhaps, for our present purposes, but which, like all similar divisions, will eventually be merged in a higher and wider scheme.

Until, however, that step is taken, we must be content to reason according to the evidence supplied by our imperfect instruments, or by our still more imperfect senses. We, therefore, recognize the difference between organic and inorganic nature, not as a scientific truth, but as a scientific artifice, by which we separate in idea, what is inseparable in fact; hoping, in this way, to pursue our course with the greater ease, and ultimately to obtain results, which will make the artifice needless. Assuming, then, this division, we may refer all investigations of organic bodies to one of two objects. The first object is, to ascertain the law of those bodies, in their usual, healthy, or, as we somewhat erroneously phrase it, normal course. The other object is, to ascertain their law, in their unusual, unhealthy, or abnormal course. When we attempt to do the first of these things, we are physiologists. When we attempt to do the second, we are pathologists.205

Physiology and pathology are thus the two fundamental divisions of all organic science.206 Each is in

205 Mr. Simon, in his thoughtful and suggestive Lectures, says, we may describe Pathology to consist in the Science of Life under other conditions than those of ideal perfection." Simon's Lectures on Pathology, London, 1850, p. 14. This is by far the best description I have met with; though, as it involves a negative, it cannot be accepted as a definition. Indeed, the context shows that Mr. Simon does not suppose it to be one.

206 In my former volume, I adopted the commonly received division of organic statics and organic dynamics; the statics being anatomy, and the dynamics being physiology. But, I now think that our knowledge is not sufficiently advanced to make this so convenient as the division into physiological and pathological, or, into normal and abnormal, provided we remember that in reality nothing is abnormal. The practically useful, but eminently unscientific, doctrine, that there can be alteration of function without alteration of structure, has effaced some of the most essential distinctions between anatomy and physiology, and especially between morbid anatomy and morbid physiology. Until those distinctions are recognized, the scientific conceptions of professional writers must be confused, however valuable their practical suggestions may be. While men are capable of believing that it is possible for variations of function to proceed from any cause except variations of structure, the philosophic importance of ana