ages. Second, that an emanation from this universal "soul of the world" was localised in each distinct organism, forming a subordinate soul, to which was committed its individual welfare through all the stages of its life, and which he seems to have regarded as the cause, both efficient and final, of its beginning, its perfection, and even of its corruption. But the animating principle of the individual organism was not, according to the great philosopher, a homogeneous entity, but a composite being; one portion of the whole psyche, the nous, or mind, being so far separable from the rest as to be capable of existing independently of the body: though, during life, in intimate union with the psyche, and forming with it the total "animating principle." These two beings, thus invented, were received by philosophising Jews, adopted by Roman sages under the names Anima and Animus, consecrated by the Fathers, illuminated by doctors of the dark ages, and, finally, appear to the popular mind-innocent of knowledge of Greek conceits-as expressions of divine truth. But though the distinction thus made between the compound Ens, in charge of the whole man, and the constituent which was invested with the glories and responsibilities of its spiritual existence, has been handed down to our days, and accepted in the popular doctrine of a conjoined "vital principle" and "mental principle", building up and actuating the body, its adaptation to the revelations of science has not been effected without extensive modification. It is now rarely held that the two "principles" are in their nature even temporarily identical. The different results of their labours in life, proved to the minds of those who believed in them that they were separate beings. The" vital principle", raised to an independent existence in the body, naturally received a further accession of dignity; its adherents could not resist its logical claims to be considered capable of preserving its individuality when its connexion with the body and the mind had ceased; and though some hesitated to go so far, and contented themselves with vague ideas that its existence was, in some way or other, dependent upon that of the body, the general result was (according to notions now in course of explosion) that the body was patronised by as many tutelar godlets, in proportion to its wants, as were the contending hosts of the Iliad; and the products of the dissolution of this imaginative partnership could be described in Horatian verse,— "Terra tegit carnem, tumulum circumvolat umbra, Orcus habet manes, spiritus astra petit."

The whole doctrine of an "animating principle" comes to us, as we have seen, from the porticoes of Athens; but the innovation which conferred immaterial rank upon the "vital principle," arose from an unwarrantable, though oftentimes unconscious, abuse of terms in

modern physiology. In the progress of research, numerous phenomena presented themselves to the investigator of the constructive, adaptive, and reparative properties of the tissues; and, as they accumulated, it became more and more obvious that they were all produced in obedience to law. It was assumed that all were referrible to one and the same energy, and as none of the known forces of external nature appeared competent to bring about effects so mysterious, a convenient expression was required, not, indeed, to define the nature of their cause, but, as was professed, merely to serve as a nominal bond of union, and to obviate the necessity of periphrasis. The metaphysician (sometimes the same person with the physician), was at hand with a long established term useful for the purpose, and "vital principle" was transplanted into the language of the physiologist, who constantly protested that he did not employ the term in any theoretical sense, but merely as a provisional name for a set of reactions of whose causative stimulus he was ignorant. The process of transferring to a denomination the properties and powers of a concrete being was once more strongly illustrated; even in the course of a single volume, "vital principle" forgot its modest rank as a vox et præterea nihil, and asserted its substantiality as "the vital principle," to be ultimately debated about and fought for with all the reverential zeal inspired by a dogma. It was not, however, to be expected that the acumen of science would long be imposed upon by a feat of verbal juggling; not only has the expression been reduced to its pristine insignificance by frequent exposure of the unphilosophical nature of the hypothesis built upon it, but the necessity of using it at all has been swept away by the discovery of the protean modifications of which the material energy is capable, by the recognition of the slight difference between some products of the laboratory and others of the organising processes, by the knowledge, that in both cases the same combinations may become the subjects of analysis and recomposition, though the products may be different; that the same polar disturbances ensue from chemical and vital reactions; that the processes are carried on in dependence upon the same physical properties, as clasticity and endosmosis, and that there is no such a thing as "inert matter," motion being the common property of inorganic and organic substances. It is true that a living cell has never yet been produced by the chemist; it is equally true, that a crystal has never been formed by magnetism, yet, we know that magnetism is but a modified form of galvanism which readily determines the formation of crystals. It is evident, therefore, that the general tendency of observation is to identify the physical and vital energies with each other, and on the other hand, no observations have been recorded essentially antagonistic to that identity.

This progress, in our conceptions of the nature of vitality, produces, amongst others, two effects important to our present purpose. Any interest we may feel in prosecuting the investigation of life to its fundamental issue is greatly invigorated, and at the same time, the probability of obtaining from that investigation a reliable result is increased or rather created; while vague notions that life processes are due to the power and intelligence of an immaterial medium were in the ascendant, it was clearly absurd, not to say blasphemous, to attempt to trace the stream of life upwards, in time, with intent to explore the hidden springs of its origin. Now, however, that the conviction is becoming settled, that life in its several organic manifestations is but the natural product of natural operations, we may, perhaps, be allowed to pursue our course uninjured by invectives such as those which have been hurled against the organic chemist for presuming to stretch his profane hand towards the sacred fount.

But, however fully persuaded we may be by physiological facts, that there is nothing in the nature of vitality which requires the intervention of a special agent, there is another class of observations which may tend to confirm, though, in itself, insufficent to form that judgment. Few subjects have excited greater interest, perhaps enthusiasm, among a certain class of experimenters, than the supposed possibility of organic formation without the preexistence of a germ. It is unfortunate for the credit of science, that the term "spontaneous generation" should have been adopted for the expression of the expected phenomenon. There are, undoubtedly, many impressed by it with the notion that science thereby attributes to organisation a power of volunteering itself into existence; whereas, all that is meant, is the possibility, that under certain conditions artificially procured, vitalisation may be set up in unorganised materials independently of known methods of germination. That such must have been, or still may be the case, more or less frequently under conditions supplied in nature, is the only logical conclusion possible to those who see in life developments but the evolution of a material force, for no reason can be given why the primal initiation of life should have taken place under laws different to those which govern its after course. The only permissible doubt, therefore, is whether those natural conditions can be reproduced by experimental arrangements. This is a problem surrounded by peculiar difficulties, in number and magnitude sufficient to tax ingenuity to the utmost. The experimenter, in brief, has not only to provide the necessary means for the production of organisms, but to effect this in such a manner as to satisfy the most captious objector that germs of all kinds were utterly excluded. It would be rash to affirm that the two requirements will never be

fulfilled; it would be equally rash to say that the approach made to the realisation of the object in view has in any instance been sufficiently near to justify the assertion of its practicability; of the many examples of extragerminal production adduced, few, indeed, have been subjected to a competent scrutiny, but the common result of these examinations-vitiation of the conclusion sought by imperfect isolation from germ-bearing media,-establishes a presumptive case against the rest. The materio-vital theory has not, therefore, received from this method of investigation an absolute demonstration of its truth; it is, indeed, probable that its general acceptation will be the result of observation rather than of experiment. But, though a

decisive answer has not been given in its favour, a candid examination of the cirumstances in which many of the experiments have been conducted, leave little room for doubt that the probabilities of the presence or absence of germs were in those cases about equal; while in a few others, the balance of evidence seems to preponderate on the side of the latter. Even if we hold that the whole of such experiments have hitherto offered no encouragement to those who relate vital effects to the productions of other material reactions, the burden of proof to the contrary, rests with those who see in the asserted failure a refuge for their destitute "vital principle." On the other hand, whatever practical reason for doubting the truth of that assumption arises from the investigation, it gives the whole of its authority to the opponents of the immaterial hypothesis. It may, indeed, be objected that the most decisive instance of extragerminal production would not, of itself, overturn the opposite opinion, unless it could be shown that the immaterial agent itself was incapable of coming into practical existence together with and under the conditions necessary to the organism appropriated to it. It will not, however, be necessary to discuss such a question seriously, until the mode in which a "vital principle" originates or obtains a settlement within an organism be definitely conceived, reasonably established, and generally accepteduntil we are educated to perceive, either, that it is by a creative act, as occasion requires, by the incarceration of one of the principles supposed by some to be floating in the air ready for use, by the continuity of the "principle" of the new born with that of the parent, or by union of the male "principle" with that of the female,—while those who are versed in the natural history of these creatures, find these little matters beyond their powers of explanation, persons of feebler imagination would not be justified in attempting the solution of problems with which they have no concern.

When, then, we become acquainted with the original source of the popular and lately scientific notion, that there exists within the body

an immaterial medium of organic life,-when we perceive that the hypothesis, at its introduction into physiology, did not even pretend to a foundation in fact, that it is surrounded with difficulties and absurdities, and that it is an utterly unnecessary mystery-making about matters purely inductive and referrible to known laws,—we cannot hesitate to condemn the hypothesis as wholly unworthy of the present state of knowledge, and further, to ascribe the origin of organisms to the modification of material force which produces the subsequent effects of generation and development. It is by no means necessary that we should be at once able to determine the exact nature of the vitalising force or forces, or to point out the other modifications of force to which it is most intimately related. We are informed by the sun's rays of the quarter in which it will rise, long before we can examine its disk; and other forces, whose modes of action are now fairly known, long baffled the investigators of their correlation. In the present case, the effects are infinitely more complex and diversified, and partial ignorance of their source is not a reproach, but a stimulus; while confidence that we are seeking in the right direction, is a strong encouragement.

But if we accept without hesitation the general truth of the proposition, that organic beings are the effects of some form of the physical force, we naturally ask, Does this offer a satisfactory explanation of the origin of mankind? Can the production, as well as the maintenance, of every degree of organisation from the vegetable monad to man, be attributed to this as its direct cause? It is from the combined testimony of geology and physiology that we can alone hope for a reply. The life-history of the earth, revealed by the former, assures us in unambiguous terms, that the life of the individual is, in its great features, repeated in the career of all natural aggregates, from the least in extent to the greatest of those whose whole course can be traced in the deposits. Each of these is seen, more or less distinctly, to have had periods of life,-cycles of development, following each other in regular succession, and homologous with those of our own birth, immaturity, adolescence, and prime, with their constant sequelæ, decay and dissolution. If, then, at several points in the existence of such groups, we perceive that it has undergone changes, which are attributable only to processes similar to those which bring about similar results in the individual life, it is difficult to avoid believing that the commencement, both of the individual and of the group, has been effected by the same methods. The life of the individual, at its origin, is simply the vitality of a single cell, which is either gifted with the faculty of so modifying the action of a uniform vital force, as to allow the development out of itself of a