In no class of facts, then, do we find a good foundation for the hypothesis of an "ideal typical vertebra." There is no one conceivable attribute of this archetypal form which is habitually realized by actual vertebræ. The alleged group of true vertebral elements is not distinguished in any specified way from bones not included in it. Its members have various degrees of inconstancy; are rarely all present together; and no one of them is essential. They are severally developed in no uniform way; each of them may arise either out of a separate piece of cartilage or out of a piece continuous with that of some other element; and each may be ossified from many independent points, from one, or from none. Not only may their respective individualities be lost by absence or by confluence with others; but they may be doubled, or tripled, or halved, or may be multiplied in one direction and lost in another. The entire group of typical elements may coalesce into one simple bone representing the whole vertebra: and even, as in the terminal piece of a bird's tail, half-a-dozen vertebræ, with all their many elements, may become entirely lost in a single mass. Lastly, the respective elements, when present, have no fixity of relative position: sundry of them are found articulated to various others than those with which they are typically connected; they are frequently displaced and attached to neighbouring vertebræ; and they are even removed to quite remote parts of the skeleton. It seems to us that if this want of congruity with the facts does not disprove the hypothesis, no such hypothesis admits of disproof.

Unsatisfactory as is the evidence in the case of the trunk and tail vertebræ, to which we have hitherto confined ourselves, it is far worse in the case of the alleged cranial vertebræ. The mere fact that those who have contended for the vertebrate structure of the skull, have differed so astonishingly in their special interpretations of it, is enough to warrant great doubt as to the general truth of their theory. From Professor Owen's history of the doctrine of general homology, we gather that Duméril wrote upon "la tête considérée comme une vertèbre;" that Kielmeyer, "instead of calling the skull a vertebra, said such vertebra might be called a skull;" that Oken recognised in the skull three vertebræ and a rudiment; that Professor Owen himself makes out four vertebra; that Goethe's idea, adopted and developed by Carus, was, that the skull was composed of six vertebræ; and that Geoffroy St.-Hilaire divided it into seven. Does not the fact that different comparative anatomists have arranged the same group of bones into one, three, four, six, and seven vertebral segments, go far to show that the mode of determination is arbitrary, and the conclusions arrived at unworthy of confidence? May we not properly entertain great doubts as to any one scheme being more valid than the others? And if out of these conflicting schemes we are asked to accept one, ought we not to accept it only on the production of some thoroughly conclusive proof-some rigorous test showing irrefragably that the others must be wrong and this alone right. Evidently where such contradictory opinions have been formed by so many competent judges, we ought, before deciding in favour of one of them, to demand a clearness of demonstration much exceeding that required in any ordinary case. Let us see where Professor Owen supplies us with any such clearness of demonstration.

To bring the first or occipital segment of the skull into correspondence with the "ideal typical vertebra," Professor Owen argues, in the case of the fish, that the parapophyses are displaced and wedged between the neurapophyses and the neural spine-removed from the hæmal arch and built into the upper part of the neural arch. Further, he considers that the pleurapophyses are teleologically compound. And then, in all the higher vertebrata, he alleges that the hæmal arch is separated from its centrum, taken to a distance, and transformed into the scapular arch. Add to which, he says that in mammals the displaced parapophyses are mere processes of the neurapophyses (p. 133): these vertebral elements typically belonging to the lower part of the centrum, and in nearly all cases confluent with it, are not

21

only removed to the far end of elements placed above the centrum, but have become exogenous parts of them!

Conformity of the second or parietal segment of the cranium with the pattern. vertebra, is produced thus:-The petrosals are excluded as being partially ossified sense-capsules, not forming parts of the true vertebral system, but belonging to the "splanchno-skeleton." A centrum is artificially obtained by sawing in two the bone which serves in common as centrum to this and the preceding segment; and as it is admitted that in fishes these two hypothetical centrums are not simply coalescent, but connate, it follows that this bisection is unwarranted, save for convenience. Next, a similar arbitrary bisection is made of certain elements of the hæmal arches. And then, "the principle of vegetative repetition is still more manifest in this arch than in the occipital one:" each pleurapophysis is double; each hæmapophysis is double; and the hæmal spine consists of six pieces!

The interpretation of the third and fourth segments being of the same general character, need not be detailed. The only point calling for remark being, that in addition to these various modes of getting over anomalies above instanced, we find certain bones referred to the dermo-skeleton.

Now it seems to us, that even supposing no antagonist interpretations had been given, an hypothesis reconcilable with the facts only by the aid of so many ques tionable devices, could not be considered satisfactory; and that when, as in this case, various comparative anatomists have contended for other interpretations, the character of this one is certainly not of a kind to warrant the rejection of the others in its favour, but rather of a kind to make us doubt the possibility of all such interpretations. The question which naturally arises is, whether by proceeding after this fashion, groups of bones might not be arranged into endless typical forms. If, when a given element was not in its place, we were at liberty to consider it as suppressed, or connate with some neighbouring element, or removed to some more or less distant position;-if, on finding a bone in excess, we might consider it now as part of the dermo-skeleton, now as part of the splanchno-skeleton, now as transplanted from its typical position, now as resulting from vegetative repetition, and now as a bone teleologically compound (for these last two are intrinsically different, though often used by Professor Owen as equivalents);-if, in other cases, a bone might be regarded as spurious (p. 91); or again as having usurped the place of another;-if, we say, these various liberties were allowed us, we should not despair of reconciling the facts with various diagrammatic types besides that adopted by Professor Owen.

When, years ago, we attended a course of Professor Owen's lectures on Comparative Osteology, beginning though we did in the attitude of discipleship, our scepticism grew as we listened, and reached its climax when we came to the skull: the reduction of which to the vertebrate structure, reminded us very much of the interpretation of prophecy. The recent delivery at the Royal Society of the Croonian Lecture, in which Professer Huxley, confirming the statements of several German anatomists, has shown that the facts of embryology do not countenance Professor Owen's views respecting the formation of the cranium, has induced us to reconsider the vertebral theory as a whole. Closer examination of Professor Owen's doctrines, as set forth in his works, has certainly not removed the scepti cism generated by his lectures: on the contrary, that scepticism has deepened into disbelief. And we venture to think that the evidence above cited shows this disbelief to be warranted.

There remains the question-What general views are we to take respecting the vertebrate structure? If the hypothesis of an "ideal typical vertebra" is not justified by the facts, how are we to understand that degree of similarity which most vertebræ display?

We believe the explanation is not far to seek. All that our space will here allow, is a brief indication of what seems to us the natural view of the matter. Professor Owen, in common with other comparative anatomists, regards the

divergences of individual vertebræ from the average form, as due to adaptive modifications. If here one vertebral element is largely developed, while elsewhere it is small-if now the form, now the position, now the degree of coalescence, of a given part varies; it is that the local reqirements have involved this change. The entire teaching of comparative osteology implies that differences in the conditions of the respective vertebræ necessitate differences in their struc

tures.

Now, it seems to us that the first step towards a right conception of the phenomena, is to recognise this general law in its converse application. If vertebræ are unlike in proportion to the unlikeness of their circumstances, then, by implication, they will be like in proportion to the likeness of their circumstances. While successive segments of the same skeleton, and of different skeletons, are each in some respects more or less differently acted on by incident forces, and are therefore required to be more or less different; they are each, in other respects, similarly acted on by incident forces, and are therefore required to be more or less similar. It is impossible to deny that if differences in the mechanical functions of the vertebræ involve differences in their forms, then community in their mechanical functions must involve community in their forms. And as we know that throughout the vertebrata generally, and in each vertebrate animal, the vertebræ, amid all their varying circumstances, have a certain community of function, it follows necessarily that they will have a certain general resemblance-there will recur that average shape which has suggested the notion of a pattern vertebra.

A glance at the facts at once shows their harmony with this conclusion. In an eel or a snake, where the bodily actions are such as to involve great homogeneity in the mechanical conditions of the vertebræ, the series of them is comparatively homogeneous. On the contrary, in a mammal or a bird, where there is considerable heterogeneity in their circumstances, their similarity is no longer so great. And if, instead of comparing the vertebral columns of different animals, we compare the successive vertebræ of any one animal, we recognise the same law. In the segments of an individual spine, where is there the greatest divergence from the common mechanical conditions? and where may we therefore expect to find the widest departure from the average form? Clearly at the two extremities. And accordingly it is at the two extremities that the ordinary structure is lost. Still clearer becomes the truth of this view, when we consider the genesis of the vertebral column as displayed throughout the ascending grades of the vertebrata. In the first embryonic stage, the spine is an undivided column of flexible substance. In its early fishes, while some of the peripheral elements of the vertebræ were marked out, the central axis was still a continuous unossified cord. And thus we have good reason for thinking, that in the primitive vertebrate animal, as in the existing Amphioxus, the notochord was persistent. The production of a higher, more powerful, more active creature of the same type, by whatever method it is conceived to have taken place, involved a change in the notochordal structure. Greater muscular endowments presupposed a firmer internal fulcrum-a less yielding central axis. On the other hand, for the central axis to have become firmer while remaining continuous, would have entailed a stiffness incompatible with the creature's movements. Hence, increasing density of the central axis necessarily went hand in hand with its segmentation: for strength, ossification was required; for flexibility, division into parts. The production of vertebræ resulting thus, there obviously would arise among them a general likeness, due to the similarity in their mechanical conditions, and more especially the muscular forces bearing on them. And then observe, lastly, that where, as in the head, the terminal position and the less space for development of muscles, entailed a smaller lateral oscillation, the segmentation would naturally be less decided, less regular, and would be lost as we approached the front of the head.

But, it may be replied, this hypothesis does not explain all the facts. It does not tell us why a bone whose function in a given animal requires it to be solid, is formed not of a single piece, but by the coalescence of several pieces which in

other creatures are separate: it does not account for the frequent manifestations of unity of plan in defiance of teleological requirements. This is quite true. But it is not true, as Professor Owen argues respecting such cases, that "if the principle of special adaptation fails to explain them, and we reject the idea that these correspondences are manifestations of some archetypal exemplar, on which it has pleased the Creator to frame certain of his living creatures, there remains only the alternative that the organic atoms have concurred fortuitously to produce such harmony." This is not the only alternative: there is another, which Professor Owen has overlooked. It is a perfectly tenable supposition that all higher vertebrate forms have arisen by the superposing of adaptations upon adaptations. Either of the two antagonist cosmogonies consists with this supposition. If, on the one hand, we conceive species to have resulted from acts of special creation, then it is quite a fair assumption that to produce a higher vertebrate animal, the Creator did not begin afresh, but took a lower vertebrate animal, and so far modified its pre-existing parts as to fit them for the new requirements; in which case the original structure would show itself through the superposed modifications. If, on the other hand, we conceive species to have resulted by gradual differentiation under the influence of changed conditions, then it would manifestly follow that the higher heterogeneous forms would bear traces of the lower and more homogeneous forms from which they were evolved.

Not only, then, do we find that the hypothesis of an "ideal typical vertebra" is irreconcilable with the facts; but we see that the facts are interpretable without gratuitous assumptions. The average community of form which vertebræ display, is explicable as necessarily resulting from natural causes. And those typical similarities which are traceable under teleological modifications, would obviously exist if, throughout creation in general, there has gone on that continuous superposing of modifications upon modifications which is displayed in every unfolding organism.

REVIEW IX.

Transactions of the Pathological Society of London; including the Reports of the Proceedings of its various Sessions from 1846-7 till 1856-7. Volumes, 8vo.-London. Printed for the Society.

Eight

THE study of pathology, for its own sake, commends itself to every thoughtful physician; and in the belief that union is strength, a Society devoted to the culti vation of this interesting branch of medical science could not fail to secure the active co-operation of a very numerous body of medical men, especially in the metropolis of Great Britain. Institutions for the special cultivation of pathology have now been established in most of the metropolitan and in many provincial towns of Great Britain, America, France, Germany, and Italy; but to Dublin, in this country, in 1830, must be assigned the merit of having been the first city in which a Pathological Society was organized. Encouraged by the success which appeared to attend the proceedings of such institutions, and invited by the pecu liar interest which invests the topics discussed at the meetings of such societies, several medical men of London met together in the month of February, 1846, and agreed upon the issue of a circular to such members of the profession as were known to be more particularly interested in pathological studies. Having received ample encouragement to proceed in this praiseworthy undertaking, a provisional committee elaborated a plan for the organization of the Pathological Society of London, as it is now constituted and named. They invited the support and

co-operation of the profession at large, not only in London, but throughout the kingdom, in prosecuting the science of pathology in every possible way, and by all means that could increase and advance our knowledge regarding the nature of diseases. At the first meeting of the Society, held on the 20th October, 1846, there were enrolled one hundred and six members. It now numbers no fewer than three hundred hordinary and nine onorary members. Its popularity as a society, therefore may fairly be considered to be increasing; and when we look at the list of those who have been its presidents and office bearers, and at the list of the officers and council elected at the general meeting in January, 1857, and finally to the members of the society as a whole, we cannot fail to perceive names the most distinguished in the ranks of our profession-of world-wide reputationmen, moreover, of the largest practice, the very busiest of doctors, who nevertheless find time to devote their attention to the highest pursuits of the science of medicine, and to work hand and hand with their younger brethren, often less favoured by the emoluments of an extensive practice.

The Pathological Society of London having been in active operation during the last ten years, it may not be considered premature if we institute some inquiry as to the results which have accrued to the science of medicine, or which are likely to accrue, from the operations of this society, as exhibited in the volumes of their published Reports. In so doing, we may perhaps succeed in giving an indication of the progress of pathological science, as set forth in the 'Transactions' before us. In them we ought to find expression given to the matured opinions which are held by the most advanced British school of pathology; and as the work of the Society mainly deals with the nature of disease as exhibited in the records of morbid anatomy, we expect to find the fullest details of all morbid appearances embracing the chemistry and microscopy of morbid products, associated with lucid clinical histories of the cases which have furnished the morbid specimens exhibited to the Society, the results of the bedside investigation of disease. On a foundation such as this we might hope to see the science of pathology, in the widest acceptation of the term, elucidated and advanced by the active co-operation of the members of the Pathological Society of London.

Whatever opinion may be arrived at regarding the work done by this Society, and the general results so obtained, there can be no doubt, when we examine the records of the past ten years, that the zeal and assiduity of the members of the Society have not diminished, but rather increased. Year after year the volumes of the Transactions' have deservedly acquired an increasing reputation. In demonstrating the practical usefulness of this Society, there is one fact in its history which strikes us as highly significant-namely, that at the first meeting of the Society for the winter of 1855-56, on Tuesday, the 16th October, the permission of the Society was sought for by the printers of its 'Transactions,' to reprint and republish the early volumes of its Reports, then out of print. A permission was of course most willingly granted, and we quote the circumstance to show the value in which the recorded works of the Society have been held.*

Those only who have prepared and arranged pathological records can appreciate the labour implied in the preparation and publication of these volumes. The chief burden of this labour has been borne by Dr. Quain, and the Pathological Society cannot be too grateful to him for his exertions to hand down to posterity an accurate account of the work that has been done. The care and labour bestowed at an early period in selecting and arranging the material of the Transactions' had an immediate, and has also had a progressively beneficial effect upon the exertions of the Society. The very appearance of the records of the material brought before the Society stimulated the members to select their cases, and to give the descriptions and histories of them with more care than at first was bestowed upon them. The evidence of this will be obvious to any one who takes the trouble to compare the first volume of the Transactions' with the

* Medical Times and Gazette.