longation in the former, from the 5th to the 7th week of its development.. How would Lord Monboddo have rejoiced in spirit, had this discovery been. made in his day! The Visceral or Splanchnic System is no less prolific in examples of the same law of structural concordance than the vascular and osseous systems. The kidney, as we have already mentioned, is multilobed in the early fœtus; so it is in the elephant, the cow, &c. The prostate gland consists of four lobes in a three-month fœtus; so it does in the horse. The uterus is bilobed in a great many of the lower animals; the same arrangement exists in the human embryo. The changes, which the external organs of generation undergo during fœtal life, are perhaps as marvellous as any of the organic metamorphoses to which we have alluded. At a very early period, there appears to be no distinction of sex; subsequently all embryos seem to be females; and at a more advanced period, the female-looking organs: appear to be transformed into male ones. All the females, at a certain period of their existence, have the appearance of being hermaphrodites; and all the males exhibit, at some time or another, that of females. Having next very elaborately pointed out the successive transformations. in the structure of the encephalon each of these transformations having its type or analogue in the permanent condition of this organ in the dif ferent orders of the Vertebrata, from the Mammal down to the fishM. Serres prefaces his description of the evolution of the alimentary passages with the following remarks : "The essential character of animal life does not reside either in the heart and blood-vessels, in the brain and nerves, or in the genito-urinary organs. An animal being may exist and live without possessing these organisms. Not so however with the nutritive apparatus. Life exists, and can exist, only on this condition that an absorption of assimilable molecules is continually going on.Hence it follows, on the one hand, that, as we descend in the scale of animal beings, we at length come to those which are reduced to a state of a mere absorbing bag or vesicle; and, on the other hand, that, as we ascend as far back as possible in our embryogenic examinations, we find the rudiments of the future man, to be nothing more than a similar vesicle. Thus, the Monad is represented, so to speak, in embryogeny by the proliferous vesicle that has been so accurately described by Purkinje; and the Volvox and Proteus by what has been called the cicatricula ovi. In the primitive embryo, as in the Polype and Entozoon, the alimentary canal has no anal orifice, nor is there any appearance of a liver or other glandular appendage. It is in the crustacea, Insects, and the Mollusca, that we first meet with such organs: the same holds true of the embryo, in what may be termed the second stage of its development. In the ulterior metamorphoses or changes, which the digestive apparatus undergoes in the embryo, other and very remarkable analogies with the permanent forms, that are present in different tribes of the lower animals, may be readily pointed out." If space permitted, we might also allude to the resemblances between the Respiratory organs in the Invertebrata, and those in the embryos of Vertebrate animals. Probably most of our readers are aware that, long before the development of proper lungs in the latter, the respiratory apparatus is essentially of the nature of gills; and that the young of certain animals of the Reptile tribe are at birth provided with the latter-to be replaced by the former at a future period of life, when the animal passes, for example, from the state of tadpole to that of the frog. Those, who wish to be acquainted with the analogical phenomena in the conformation of the early human embryo, should consult our author's description. 179 There still remain one or two other topics introduced and commented on in this truly original work, to which we would solicit our readers' attention for a few moments, before drawing our remarks to a close: and, first, of what M. Serres calls the Gradation of Tissues in Zoological and Embryological Formations. "The primary or elementary tissue," says he, "in the lower Infusoria, as in the embryo during the first stage of its existence, is mere cellular substance, modified in a variety of ways. This is the common basis, so to speak, of the Monad, the Volvox, the Acephalocyst, the Ascidia, and of part of the Echinococcus and Polype. The essential properties of this tissue seem to be-1, a uniformity of function, limited to exhalation and absorption; and, 2, a power of independent existence, when a portion is detached from the rest. If to this tissue be superadded a peripheral system of blood-vessels, we advance one step in the animal scale, and come to part of the Echinodermata. If a muscular system be then added, we reach the Rotifera; and, if all these systems be combined, we arrive at the Helianthoidea. Whenever the muscular tissue is distinctly developed, we find that traces of a nervous apparatus-hitherto so blended and confused with the different parts of the animal body as not to be recognisable-begin to appear; as we observe for the first time in the Annelides, the Mollusca, and perhaps also the Crustacea. Now, a very striking analogy may be traced between these progressive gradations in zoological development and the successive changes that are discoverable in the evolving organization of the embryo. Before impregnation, the animal is represented by a mere vesicle that consists altogether of cellular membrane enveloping an oleaginous fluid. After impregnation, the blastoderm-from which proceed the constituent parts of the embryo-exhibits two membranes; one external and serous, and the other internal and mucous. In a short time, a vascular tissue is found to be interposed between these two; and subsequently a nervous tissue makes its first appearance." Some light has been unexpectedly thrown on this subject by the results of certain experiments, which M. Serres has recently performed on worms and leeches." The common earth-worm," he remarks, "is very different, it is well known, in its formation, from the Polype, the Tænia, the Helianthois, or the Arenicola; but, if we follow out the various metamorphoses which the animal undergoes before it arrives at its complete development, we find that it actually does resemble each of these creatures successively, according to its epoch of evolution. Now what is very remarkable is, that a counterproof of these successive advances or elevations of structure is afforded by watching the process which Nature follows in effecting the regeneration of a part, that may have been artificially destroyed. The first act of regeneration in the new-formed portion reproduces exactly the structure of an Arenicola; the second act (supposing the new-formed has been again destroyed) reproduces that of the Helianthois; while the third and last act degrades or brings the part down to the structure of a Polype. It is obvious, therefore, that the reproductive *M. Serres mentions that, while conducting these experiments on earth-worms, he quite satisfied himself that many of the alleged different species of this and other Invertebrate animals are, in short, but the same species, only at different stages of their development. The most advanced development is the ideal type of the genus; and the least advanced constitutes the last species of it. mark is, in an especial manner, applicable to the case of the Infusory animalcules, which have too often been most unnecessarily grouped into a great number of different families. power becomes gradually more and more feeble, just in the same manner as we observe that the reproduction of the organic tissues in the human body become exhausted, in any part, by a frequently-repeated act of regeneration. This may be not unfrequently seen in cases of old ulcers. A first, a second, and even a third cicatrization gives birth to a new structure that is resistant, and approaches in its characters to the normal condition of the part; but, if this act of reparation be repeated more fre quently, the new-formed tissue becomes less and less completely organized the ulcer is then said to be atonic, and under such circumstances it often remains incurable. The same remark is applicable to tuberculous formations, which occur in the lungs and other parts of the body." He proceeds to point out certain analogies that may be traced between the imperfect or irregular developments-in other words, the Monstrosities -that not unfrequently occur in the human embryo, and the normal structures in some of the lower animals. We must confine our notice of this curious subject to the giving of one short extract. "These mutilations or privations of organs are incompatible with the continuance of the independent and extra-uterine life of the foetus; but, although this be quite true, let it not be forgotten that, despite the presence of such imperfections of organization, the creature was alive while it remained in the womb and was attached to the mother. Nay more, it may already have passed through several stages or phases of existence, and have perhaps more than completed its term of life as an Invertebrate being. Few physiologists seem to be aware that there is in these monstrous or deformed productions a scale, so to speak, of uterine viability (capability of life)-a circumstance of high philosophical importance, as it tends to show that there is a sort of independent existence on the part of the embryo, during its intra-uterine life. Thus, a fœtus that is destitute of an extremity only, will continue to live much longer within the womb, and thereby acquire a much higher degree of development, than another in which the heart or the brain is wanting." In drawing these remarks to a close, we cannot but express a hope that they may excite the curiosity of some of our readers, and induce them to examine, more minutely for themselves, the highly interesting subject of Embryology in connection with that of Comparative Anatomy. No medical man can be said, in the present day, to be duly educated, if he has not acquired a tolerable knowledge of the latter science. How should it be otherwise, when we consider that Physiology can never be studied as it ought to be, without a constant reference to the organization of all classes of animals, from the simplest Zoophyte up to Man himself? He is but the last link of the chain that extends unbroken through the long series of zoological formations, and every part of which, however dissimilar and unlike one may seem to be from another, is constructed upon a simple harmonious and kindred plan. The marvellous discoveries that have been made, of late years, in Embryology, have added not a little to the interest of this subject, and have brought to light many such unexpected analogies and features of resemblance between forms that had been hitherto imagined to be most unlike, as almost to warrant the startling ob servations of our author, that "Human Organogeny is only a sort of transitionary Comparative Anatomy, as in its turn Comparative Anatomy is only the fixed and permanent condition of the different phases of Hu man Organogeny ;" and that "Animals, in a genetic point of view, may be regarded as the permanent embryos of man.' In contemplating the succession of phases, or stages of development, which the human being is found to exhibit during its evolution within the womb-commencing in the most simple, and terminating in the most complex form, when it reaches its mature and complete formation--are we not almost involuntarily reminded of that most interesting discovery of modern Geology, viz that just in proportion as we trace back the history of the earth in its physical structure, by examining the older and deeper strata of its formation, so, it would seem, the more simple and uncomplicated were the forms of animal beings then in existence? In the transition rocks we meet with the fossil remains of the very lowest tribes only; in the secondary, the remains are of animals of a higher order; and it is not until we reach the more recent deposits that the bones of the mammalia are ever found. Is it not possible to trace here a sort of parallelism between the genesis of animal beings during the successive epochs of the world's formation, and that of the embryo during its successive gradations of evolutionary development? The thought is but a passing fancy: and as such only we give it. But, whether there be any truth in the conjecture or not, of this we may rest assured, that the more that we search into the hidden workings of Nature, and make ourselves acquainted with her teeming wonders, the more clearly we shall perceive a unity of design and a simplicity of operation pervading all created things, and the more strongly shall we feel that they have all been fashioned and ordained, and that they are all upheld and continued, by one Almighty hand. It has been beautifully said that And so it is with the still greater marvels of the animated world. The same law, that presides over the formation of the humblest creeping thing, directs the development of him who walks the earth "With port sublime, and hopes beyond the skies." All are alike framed on one simple and universal plan ; all are created from a few, and the same simple elements; all perform similar functions; and all at length become resolved into the same component parts. Ought not the study of such a theme as that which we have been glancing at, while it exalts our admiration of the supreme wisdom and power of the Divine Architect, to serve at the same time to humiliate the pride and arrogance of man? In his body he is but a step removed from the brutes that perish; and, at one period of his existence, he has been but as they. His structure is not more wonderful than theirs; his physical powers are in many respects inferior. It is the spirit within that alone stamps him with pre-eminence, and lifts him so far above every other earthly thing "wherein the breath of life is." Admirably hath the poet expressed the antithetic constitution of his nature-physical as well as moral-when he exclaims How poor, how rich! how abject, how august! How complicate, how wonderful is Man! An heir of glory! a frail child of dust! A TREATISE ON THE USE OF THE SYMPATHETIC NERVE AND ITS GANGLIONS, WITH THEIR INFLUENCE ON VARIOUS DISEASES OF THE ABDOMINAL AND PELVIC VISCERA. By T. Proctor, M.D 4to. pp. 48. Highley, 1844. WITHOUT going so far as to say he has completely made out his case, we think the author of this interesting essay has brought forward facts and opinions in reference to the functions and morbid affections of that portion of the nervous system, concerning which the most vague, unsatisfactory, and contradictory doctrines have hitherto prevailed, that must command attention and will stimulate observation by directing it into a more definite channel. That additional and multiplied researches will be required be. fore what he has advanced can take the position of an assured fact, he does not endeavour to conceal; and, having made what must at the very least be termed a most happy suggestion, he contents himself with pointing out a few corroborations which the phenomena of disease and the action of remedies seem to supply. If more extended observation confirms the view set forth, the practical consequences will ere long exhibit themselves abundantly enough. The contemplation of the intimate anatomical relations of the sympathetic nerve with the arterial system, induces Dr. Proctor to conclude that its office consists in regulating the contractility of the blood-vessels. Nerves derived from other sources frequently accompany arteries for a long portion of their course, never, however, transmitting branches large or small to them, so that their juxta-position must be referred to some other cause than for affording facility for influencing their movements. The sympathetic, on the contrary, is emphatically the nerve of these vessels, enmeshing and penetrating them on every side, and following their minutest ramifications to their ultimate distribution. After describing the anatomical relations of the nerve, Dr. Proctor thus proceeds : "The nearest approach to a positive determination of its use that we can come to with our present limited knowledge is, that it is for the purpose of regulating the tonic contraction of the arterial system, and for nothing else; however, it is difficult to expound or afford the requisite proofs of this opinion, nor am I aware that public attention has at all been called to it. I venture, therefore, allowing this idea to form the basis of my investigation, to proceed to explain my present views upon the subject, first calling the reader's attention to the remarkable fact |