bodies of those bones. The lateral arch of the second, which is the largest, forms a chord of seven or eight lines. At the age of one year, those processes are united, so as to form a ring in all except in the first two cervical, and in the lumbar, vertebræ; and in the bones of the sacrum. At two years and a half, the union is completed in the transverse processes of the first and second cervical, in the last of the lumbar vertebræ, and in the inferior bones of the sacrum. At five or six years of age, the whole have perfectly united.

Merely pointing out one instance of the utility of their application, we may remark, that the facts last mentioned (many of which, however, were previously known,) will explain the peculiar appearance of spina-bifida, and the reason why it usually occurs in the situation of the lumbar vertebræ. They will shew why the tumor containing a fluid should appear in this part, when the disease on which it depends is often seated in the brain, or throughout the whole extent of the spinal marrow.

The observations of M. Beclard on the formation and development of the cranium, possess a great degree of individual interest; but we pass them over in consequence of this part of the subject having been pursued to a greater extent by Hr. J. F. MECKEL, of Halle, whose Memoir (3) on it is now to become the object of our attention.

These researches were, apparently, instituted in consequence of some curious ideas deduced from observations made in comparative anatomy; and they seem to have developed a physiological principle that may be applied with considerable benefit in the practice of medicine. It is this: that the vertebral column and the cranium perfectly correspond with the organs they enclose, not only with regard to form, but also in the manner in which they are developed. As the vertebral column is formed of annular or discoid bones piled on each other, so we may represent to our mind the spinal marrow constituted of spherules of nervous matter, from each of which is derived a pair of nerves, and each of which corresponds with an individual vertebra: the number of the pairs of nerves also equals that of the vertebræ, and each pair escapes from the vertebral canal between two of them. Each segment, as well of the bony column as of the nervous mass, possesses its proper vascular system; and as the vertebræ are chiefly formed of two lateral portions, so is the spinal marrow composed of two longitudinal cords applied laterally to each other.

There exists between the cranium and the encephalon, the same relation that we have noticed as existing between the vertebral column and the spinal marrow. The bones which

(3) Journ, comp, du Dict. des Sciences Med. tome ii.

compose this extensive vase correspond in their position, their division, and the mode of their development, to distinct portions of the organ which they enclose. We cannot enter into a particular account of the observations of Hr. Meckel in support of this statement, but we must remark, that he appears to have satisfactorily demonstrated its truth. This distinguished anatomist supports a curious proposition, which OKEN advanced above ten years since, and which M. Beclard has also illustrated, that there is a similarity or relation between the different bones of the cranium and the vertebræ : a certain division of each corresponding with a distinct portion of the other, both in the form and the mode in which they are developed.

This notion appears to be a further prosecution of some curious ideas lately advanced by several eminent anatomists respecting the origin of the brain, which are now generally admitted in Germany, that it is a production of the spinal marrow; (4) and the reflections to which this opinion gives rise have probably contributed much to raise up the doctrines respecting the cerebral functions now prevalent in that nation. We shall not expressly point them out, for reasons which those who perceive what we allude to will easily recognize; but our duty as an historian obliged us to relate the observations which led to this remark.

Hr. Meckel in the same memoir enters into a particular consideration of the mode in which the whole of the osseous structure surrounding the three centres of the nervous systems is developed; but we cannot adduce any further observations which, in an isolated point of view, would be interesting to the Teader.

We can only speak in general terms of a Treatise by M. GEOFFROY SAINT-HILAIRE, on the anatomy of the osseous structure of the respiratory organs. (5) This work will be perused with extreme pleasure by naturalists as well as by physiologists. The author has elucidated, in a very clear and ingenious manner, a law in the economy of nature which is again becoming generally admitted by philosophers: that the animal powers and functions are developed in proportion to the wants of the individual; or in the words of an Epicurean,

Nihil ideo quoniam natum est in corpore, ut uti
Possemus; sed quod natum est, id procreat usum.

M. St.-Hilaire also proves, with regard to structure, that in

(4) For a general view of this subject, see C. G. CARUS; Versuch einer darstellung des Nervensystems, und insbesondere des Gehirns, nach ihrer bedeutung entwickelung und Vollendung im thierischen organismus. Leipzick, 1814.

(5) Philosophie Anatomique des Organes Respiratoires, sous le rapport de la determination et de l'identité de leurs pièces Osseuse; par GEOFFROY SAINT-HILAIRE. 8vo. pp. 560; avec un atlas in quarto de 10 planches. Paris.

all vertebrated animals nature has followed a general plan, some points of which have only been varied in the different species; and that the passing from one form to another, in similar organs, is effected only by almost insensible gradations.

This proposition appears to have been first developed and illustrated by SPIX; (6) although it was probably founded on the views which OKEN (7) had taken of the analogy existing between the spine and cranium.

Those observations, with several other original and ingenious propositions, are elucidated in a very forcible manner by M. St.-Hilaire, whose work, though confined to only a few objects, constitutes an highly valuable addition to modern literature on natural history.

M. SERRES has been also engaged in researches on this part of descriptive anatomy. A Memoir which he lately presented to the Academy of Sciences of Paris, on the laws of osteogeny, treating especially on the formation of the articular cavities, evinces the same accurate and ingenious views in this enquiry that gave so interesting a character to his former productions, But we may avoid the necessity, and indeed the utility, of giving a particular account of his observations, by referring our readers to the papers of Mr. HowSHIP on the same subject, in the eighth and ninth volumes of the Medico-Chirurgical Transactions, who has prosecuted it in a more particular and extensive manner, and on similar views with those which guided M. Serres.

We never contemplate the productions of the learned and ingenious MECKEL, without regretting that he was not a compatriot of, and contemporary with, our HUNTER: the latter would not then have been doomed to pursue his researches silent and alone, unknown to the world except by their results, and those for a long time undervalued, because their merit was not discerned he would have cherished with delight the genius of the German philosopher, whose talents and society would have assisted and cheered his solitary labours.

We shall adduce only a few from amongst a multitude of analogous observations, contained in a Memoir by Professor Meckel, (8) on the formation of the intestinal canal in the mammiferi, and particularly in man, which will show those who imagine minute anatomical research to be dull and useless, how delightful it becomes when directed by physiology, and how many facts may even now be discovered which will illustrate pathology, and consequently contribute to the improvement of the medical art. The first series of extracts will elucidate the cause

(6) Cephalogenesis, &c. Munich, 1815. fol.

(7) Uber die Bedeutung der Schaedelknochen. Jena, 1807. 4to. (s) Journal comp, du Dict. des Sciences Med. tome ii.

of the frequent appearance of umbilical hernia in the foetus, and in the infant at the period of birth.

"The intestinal canal," says Hr. Meckel, "presents many changes in its situation at different epochs in the life of the fœtus. Although in its origin it is attached to the vertebral column, and is at first entirely straight, it is certain that, at a more advanced period, (which is, however, still very near the instant of its origin when compared with the whole life of the foetus,) it is more separated from it, relatively speaking, than it is at any subsequent period during the whole course of its existence; that is to say, it passes out of the abdominal cavity in the place which is afterwards to become the navel, and, passing through the opening there observed, it is engaged in the umbilical cord." "I have always found a portion of the intes tinal canal engaged in the funis umbilicalis, until the commencement of the third month, (meaning, after it has separated from the spine,) although the embryoes that evinced this appearance did not shew the smallest trace of irregular conformation in any other point of their organization." In a great number of the mammiferi, especially in the goat, the sheep, the cow, the pig, and the rabbit, I have always found, at a certain period, the greatest part of the intestinal canal in the umbilical cord. The same fact has been observed by EMMERT, HOECHSTETTER, and PALETTA."

The correctness of these observations is, however, disputed by OSIANDER :(9) he says, that in all cases where this projec tion of the intestinal canal from the cavity of the abdomen is witnessed, and at whatever period it may occur, it is to be considered as a state of disease. But we rely on the extent and accuracy of the observations of Hr. Meckel, and are disposed to admit the occurrence of the fact in the manner in which he has stated it.

"At first," says this anatomist, "we only see we only see springing out a small portion, forming an acute angle; but this by degrees increases in bulk, and forms several convolutions. At the epoch when these convolutions manifest themselves, we see the coecum appear in the form of a little tubercle, with its extremity pointing anteriorly: it is situated on the inferior side of the angle, and never on the angle itself." "By degrees the circumvolutions approach each other, the hernial portion is converted into a more rounded projection, situated immediately within the umbilical opening: this gradually contracts, and the cavity of the cord which contains the hernial portion of the intestine becomes separated from the abdominal cavity by a more pronounced contraction. The intestine insensibly re-enters into

(9) SALZBURGER Medicinisch-Chirurgische Zeitung. No. 89. 1814.

the belly, the colon passing first, and the small intestine afterwards." The meso-colons after this gradually contract, until they assume nearly the proportion they afterwards bear to the dimensions of the relative organs.

It is evident that the accidental want, or later occurrence, of those various changes in the structure of the parts above described, will cause the appearance of umbilical hernia at the time of birth; and we cannot be surprised at its frequency, when we contemplate the nature of the process by which it is ordinarily prevented. The same observations, especially the gradual contraction of the meso-colons, will explain why, with a few exceptions, those hernia at length spontaneously dis

appear.

We shall now adduce some extracts respecting the development of the structure of the alimentary canal appertaining to the exercise of its proper functions.

"The villosities of the stomach appear at a very early period," observes Hr. Meckel, "but they pass through several degrees of evolution which merit being remarked. It is at the commencement of the third month that I have begun to perceive them distinctly. The internal surface of it is then rendered unequal by several longitudinal folds, strongly marked, pressed against each other; but of which, however, the free part is hardly rugous. By degrees, the number of these folds, their depth, and the quantity of ruga, increase, so that at the end of the fourth month, sometimes earlier, we find, instead of simple longitudinal folds, a multitude of little elevations disposed without apparent regularity. The intestinal villosities, then, derive their origin from the ruga, which manifest themselves gradually and in progression in the simple longitudinal folds. Another circumstance worthy of remark, is, that we find them at first much more diffused than they are at a subsequent period. Indeed, they are met with throughout the whole intestinal canal until the seventh month. The valvulæ conniventes appear much later than the villosities. Not the least trace of them is found until towards the seventh month. They then appear under the form of slight elevations, which disappear with great facility when the canal is a little stretched. The canales choledochus and pancreaticus, are always separate in the first. instance. The pancreatic canal opens by a round tubercle into the left side and upper part of the descending portion of the duodenum. The orifice of the canalis choledochus is situate much lower, and on the right side of the intestine. The two orifices are much larger than they are at a subsequent period; and they gradually become united: this occurs soon after the middle of the third month. I have never seen the smallest trace of the pylorus before the expiration of the fourth month."