tering upon his subject, Mr Brodie seems fully aware of the disadvantages under which he labours in performing the arduous duties of the office, which he has been so handsomely solicited to fill.—“ I cannot," says he, "but be aware how difficult, and how extensive is the science of which I am about to treat; and I am also conscious of the imperfect nature of my own qualifications," adding, "that his knowledge of it, is no more than can be acquired by an individual who joins the pursuit of science with that of an arduous profession." These difficulties too have perhaps received some augmentation from his being the immediate successor, in the lectureship of a gentleman, who, though he has been very severely, but somewhat justly, 'censured, for rashly indulging in speculations foreign to his purpose, is, nevertheless, admitted to be a man of high professional character, and of acknowledged ability and genius.

It is the object of Mr Brodie, in the Lecture before us, to treat" of the Laws which regulate the Phenomena of Life, and the changes which Matter undergoes, and the forms which it assumes, when it becomes associated with this mysterious and active principle;" and he seems desirous, after the example of Baron Haller and Mr Hunter, to refer "the phenomena of life to peculiar laws, instead of explaining them as had been done before by the mechanical and chemical laws which operate on dead matter.” He admits, that matter, when endowed with life, does not lose those properties which belong to it in its inorganic form;" and adduces many instances in support of the assertion, though he considers such properties as being in combination with others; and that the changes "which are consequent to death, shew not that they are suspended, but that they are modified and counteracted by the influence of another principle.' His great object seems to consist in a desire to prove that the laws which govern life differ from those "which govern the changes of inorganic matter;" and we think, that through several pages, he has argued the question with great apparent probability and clearness: we do not, however, quite agree with him when he seems to infer, from certain examples which he produces, that life

may exist in a kind of dormant state, independant of any active principle; and we think no one of his instances conclusive on the subject. "In general," says Mr Brodie, "we see life combined with action, and living beings present an endless multitude of phenomena in perpetual and rapid succession. Life, however, may exist independent of any action which is evident to the senses. The egg continues unaltered, and giving no sign of an active principle within it for days and weeks; but its vitality is demonstrated by its resisting putrefaction; and when subjected to the influence of a higher temperature, it begins within itself a series of changes, which end in the developement of a new animal. The seeds and bulbous roots of plants are under parallel circumstances; and trees are frost-bound in the winter, and put forth new leaves and blossoms in the ensuing spring. A leech, which was immersed in a cold mixture, was instantly frozen into a hard solid substance; at the end of a few minutes the animal was gradually thawed; the leech revived, and continued to live for thirty-six hours after the experiment. A curious illustration of this subject is afforded by the animalcules which occasion the blight in corn, called by farmers the purples or ear-cockle. These animalcules, which are not to be discerned by the naked eye, become distinctly visible when moistened with a little water, and placed on a piece of glass in the field of a microscope. They are seen in constant motion, and even the ova may be detected in the act of escaping from the oviduct. If the moisture be allowed to evaporate, a dry stain is left on the glass, which is scarcely perceptible, but, on the addition of a little water, the animalcules revive, and, move briskly as before. This experiment was repeated by Mr Baüer with the same animalcules at intervals of several months, during a period of more than six years, and always presented the same phenomena." Among the foregoing examples the experiment of the leech is, perhaps, the most favourable to Mr Brodie's supposition; but here, it appears to us probable, from the short time during which the leech remained in a frozen state, that the active principle was not completely destroyed, and consequently that little

or no conclusion can be drawn from the experiment. In the instance of the egg, our author does not appear to be aware that a very sensible degree of warmth exists in what has been called the "cicatrice" of an egg not in a state of putrefaction; this warmth is felt more decidedly in fresh laid eggs, than in those which have been lain for several weeks; and any of our readers may convince themselves of the truth of this, by simply pressing the larger end of an egg to the lips. It is by this test that the farmer's wives in some parts of England learn to distinguish a good egg from a bad one. Experiments, as to the real existence of heat, cannot well be tried with respect to the purple, or ear-cockle; but, reasoning from analogy, we should feel in clined to believe that the active principle was never " annihilated," in the experiments made by Mr Baüer, although, from the extreme minute ness of these animalcules, it would be difficult, if not absolutely impossible, to detect its existence. As to the "bulbous roots of plants" and "trees frost-bound in the winter," we should draw a conclusion opposite to our author, even from the fact he has himself noticed in a subsequent part of his lecture; for if, " In the midst of a long-continued frost, a thermometer introduced into the centre of the trunk of a tree does not sink to the freezing point," and again, if, "The temperature of the interior of a tree is said to be above that of the atmosphere, if the latter be below 57 of Fahrenheit's thermometer," and "if the temperature of the atmosphere rise above this point, that of the tree does not rise in the same proportion." To what possible cause can these phenomena be assigned, unless to the absolute exist ence of some active principle, which enables the tree so powerfully to resist these various degrees of heat and cold in the external atmosphere? especially as, we believe, no such power of resistance is observable in a tree actually dead. In remarking on the foregoing examples, we do not mean to deny the possibility of Mr Brodie's supposition, however we may think them insufficient to prove the accuracy of his notion. He proceeds to some of the most remarkable circumstances incident to life in" its active state," and gives a very admirable account of the elements that

enter into "the composition of all living bodies," and of the wonderful effects produced in the structure of living things, by the various combinations of a few simple materials, and the chemical changes they undergo; "and on the influence of the living principle."

In speaking of the blood, we do not exactly comprehend the author's meaning, when he tells us, that "The blood is necessary to life, inasmuch as it supplies to the different organs that, without which life cannot exist-but no farther;" and yet, immediately after, gives the instance of a frog, that lived and crawled an hour after the excision of the heart, “by which time, the vessels must have become empty of blood." Again, he says, "life, in its active state, exists no where, except where there is access to the atmospheric air;" but, if this be true, and we believe it to be so, what possible effect can the air have on an animal, when it has been entirely deprived of the only me→ dium through which the air can have any influence; and may it not be more reasonable to conclude, in the instance adduced, that the blood was never completely exhausted till the animal ceased to exist? It is well known that the animals, instanced by Mr Brodie, are capable of existing for months, and even for years, in a state of torpidity; and hence, may it not appear probable that they are able to carry on a kind of temporary life, after they have been almost entirely drained of blood? The real nature of this most important fluid is, and probably ever will remain, one of the most difficult questions in physiology; and, perhaps, the author may be less clear on the point than usual, from his possessing some different, though indistinct views of the subject, which, in the present imperfect state of the science, he has wisely abstained from producing.

Our limits will not permit us to follow him throughout the whole chain of his admirable reasoning, on the great question of a "particular creation ;"his arguments, in support of it, appear to us to be conclusive, and absolutely unanswerable. It has been asserted by some writers, from what is known of the nature of parasitic animals, and from other instances, "that there is in nature the power of forming the lower orders of living beings by an equivocal

generation," and that " dead matter is, under certain circumstances, capable of bursting into life, where life before did not exist." To these suppositions Mr Brodie offers the following objections: "These same animals, when once called into existence, are endowed with the generative faculty, and bring forth young in the usual manner. Is it probable that the origin of the parents should be different from that of their offspring? Is it not more reasonable to conclude, that something respecting the production of these minute creatures is concealed from our view, than that they should be produced in a manner entirely contrary to the analogy of what is observed in other beings endowed with life, whose larger size makes them more fit subjects of observation? It is not difficult to believe that their ova may be too small and insignificant to be cognizable to our senses-that they exist where their existence is not suspected; and that it is only when conveyed by accidental circumstances, into a proper nidus, that they give birth to the young ani mals."-Page 27.

The succeeding twenty pages are chiefly devoted to proving," that an animal is something more than a mere assemblage of instruments, which are connected and act in concert with each other." We shall not attempt to remark on this part of the lecture, except by stating generally, that for accurate investigation, sound judgment, and perspicuous reasoning, it has rarely been surpassed; while the simplicity of the style, the total absence of all af fectation, and the feeling with which the whole is written, throw a charm around it not often possessed by works on similar topics, otherwise containing great intrinsic excellence. Mr Brodie's opinions, on these subjects, form an admirable counterpoise to many prevalent notions of the day, and do no less credit to the soundness of his understanding than to the excellent qualities of his heart. Some objections may possibly be raised to the want of a methodical arrangement of his sub

ject; but, on this point, we shall leave our author to speak for himself.

"We cannot, as in some sciences, set out with what is most simple, and gradually ascend to what is complicated. In considering one set of phenomena, I shall often have occasion to refer to others, which I have not had an opportunity of explaining, and I shall feel it difficult to say all that I would wish to say on these subjects, without supposing my audience to be already possessed of a general informa tion respecting them. This, I am anxious to state in the commencement of the course, as an apology for many things in the subsequent parts of it, which might otherwise be attributed to a want of method, and a careless arrangement."

Towards the close of the Lecture, a warm and just eulogium is pronounced on the deep research and splendid powers of Mr Hunter, who seems to have been the first philosopher who emancipated the science of physiology from the "clumsy mechanical, and chemical notions," under which it had so long laboured. The concluding sentences of the Lecture cannot be too often, nor too seriously reflected on, by those whose business it is to devote their time and abilities to the study not only of surgery, but of its collateral branches, on the attainment of which, so mainly depends the dignity of the profession, and the rank it must hold in society. We suspect, that, in these observations, Mr Brodie writes from the experience of his own professional career; and, if the distinguished situation he holds, at an early age, be the result of the study and persevering course which he has undeviatingly pursued, from the commencement of his public life, we hope it may prove a sufficient stimulus to others of his profession, zealously and vigorously to follow his animating example, in making strenuous endeavours to throw additional lights upon an art, which is of such vital importance to the comfort and happiness of human nature.