varies exceedingly at different times and in different animals; and hence a long-continued and diversified train of research is necessary, before we can be authorised to propound any general assertions. So necessary is it to be on our guard, in all enquiries into the operations of life, that we shall frequently commit grievous errors, if we hazard even a single induction from a few experiments; there is an apt illustration of this in the topic which we are now considering; it has been stated, only a few lines above, that the quantity of azote was found augmented in respired air; now this holds true at one season, and not at another. From October to February, or thereabouts, Dr. Edwards discovered that there was, in reality, a diminution, and, consequently, an absorption of azote; his opinions are founded on a most extended suite of investigations on different animals. He says

“If the difference between the inspired and expired azote had been quite irregular and confusedly scattered throughout the course of the experiments, no reliance could have been placed in them, but on the other hand, when we see these differences, however slight, constantly bearing for a considerable period in one direction, and then having an opposite tendency during an equal space of time, notwithstanding the identity of the mode of experiment, we cannot but conclude that a real change has taken place in the subject under investigation." 224.

Humboldt and Provençal, in their long series of experiments upon the respiration of fishes, have proved that these animals absorb a large quantity of azote. Spallanzani asserts the same of reptiles, and of many other animals. On the other hand, Bertholet, Nysten, and Dulong have most unequivocally found, on some occasions, an excess of this gas. How shall we reconcile these contrarieties? This is, perhaps, not so difficult as may at first be imagined; let us only suppose that there may be continually going on, in animal bodies, as absorption and an exhalation at the same time; and then the mere predominance of the one function over the other explains away all our difficulties. But let us proceed cautiously, and first ascertain whether any unequivocal mode of trial may be devised, to prove that azote is really exhaled from an animal :-Now all that we have to do, is to place an animal in an atmosphere of oxygen and hydrogen; Allen and Pepys acted on this plan, and they have most distinctly shewn that the exhalation of azote was frequently so great, as to exceed the bulk of the animal; and that there was also a considerable absorption of hydrogen. Here, says Dr. E. is a proof that two functions are performed at the same time, and is a key to the observation above made, that in different cases, according to diversified circumstances, we may find equality, excess, or diminution in the azote expired, when compared with that which has been inspired. As yet, we have not spoken of the probable manner in which the carbonic acid, which is thrown off from the lungs, is generated-whether it is evolved as a gaseous exhalation from the blood, or whether it results from the oxygen of the atmospheric air combining with free carbon, through the thin membranous coats of the vessels. A simple experiment determines this question :-If an animal be made to breathe a gas which does not contain any oxgen, and if more carbonic acid is found than can be accounted as being the residue which may exist in the lungs, at the time of subjecting the animal to the trial, we are forced to the conclusion, that the acid has been evolved in a gazeous form. Now let frogs (especially in Spring, when,

as we formerly shewed, their irritability, or organic vitality was most energetic,) be confined in vessels containing hydrogen, they will be found to live for 8 hours, and upon examination the air will be found to contain carbonic acid in a much greater quantity than that of the lungs could hold. If this experiment be performed in the warm weather of Summer, or of Autumn, the frogs will not live above one half the time; another apt illustration of the doctrines previously unfolded. Similar results were obtained by introducing fishes (cyprinus aureus, or golden fish) into vessels containing pure hydrogen. Carbonic acid was readily detected; and Spallanzani's experiments assure us, that the same holds good of snails, and other mollusca. Dr. Edwards extended his observations to kittens, and other very young animals, and concludes that the principle is of universal application, and that the carbonic acid in expired air is due to exhalation, and that it proceeds wholly, or in part, from the blood. Vauquelin, Vogel, Brande, and Sir E. Home, have proved that it does exist in the mass of blood, and may be disengaged from it when the vessel which contains it is placed in hydrogen gas.

We have now brought to a close our analysis of the experimental researches of Dr. Edwards, on the influence of some of the most important physical agents on the life of man and other animals; but something still remains to be done; and we must enquire whether the additional and more exact knowledge we have obtained can be made available by the medical man in the prevention and cure of diseases. We are not, indeed, of that number, who estimate the value of physiological discoveries, only by their immediate and very obvious practical applicability; but would rather regard every step which is made in the investigation of the mysteries of living bodies, important, per se, as a fresh fact added to our knowledge, and also as tending to elucidate the working of the whole machine; if such be the case, it needs not the sagacity of a prophet to foretel, that just in proportion to the correctness of this knowledge must be our hopes of rectifying the machine when out of order, and of keeping it unharmed from losses and injuries. We have left ourselves little space for alluding to the application of the foregoing discoveries in detail; our remarks must therefore be brief and concentrated. Dr. Edwards is of opinion, that during natural sleep the faculty of generating heat is considerably impaired; and in this manner he explains the common observation, that a cold which is not inconvenient to us while awake, is hurtful if we are exposed to it during sleep, and how intermittent and other fevers so frequently arise in ships and camps from the night fogs. The following remark is exceedingly interesting, and offers a most ingenious hyphothesis on what are vulgarly denominated "trances."

"Natural sleep, in many species of hibernating animals, merits the denomination of lethargic sleep, from the remarkable diminution of temperature, respiration, and circulation, as well as of the external motions and excitability of the senses. It differs in intensity according to individuals and species. We have shewn the modification of the constitution which has the greatest influence in this respect; so that it will be easily imagined, that changes of this kind may take place in man, which will render his sleep lethargic, which state, however, is not to be confounded with the effect of disease or accident, such as privation of air or exposure to noxious gases. Instances of the lethargic sleep here alluded

to, are to be found in medical works, and are apt to be regarded as fabulous, but my own experience has convinced me, that such cases do occur." 248.

Dr. Edwards alludes to the propriety of clothing very young children more warmly than adults; their power of producing heat having been proved to be inferior. In some fevers, those which Torti has designated "febres intermittentes algida," this power appears to be so much weakened, that the patient dies in the cold stage, the system being unable to recover its loss of heat.

As a general rule, vapour baths are to be preferred to those of warm water, on the principle that the vivifying action of the air may be conjoined with the softening effects of the warmth on the skin. As a proof that the exclusion of the surface of the body from the contact of the air may be injurious, we need only refer to the cases of many persons experiencing a difficulty of breathing whenever they employ a warm water bath. The same reason explains the faintness which results from remaining too long in the bath and it will be readily conceived that these effects will vary in different individuals, according as the pulmonary respiration has a greater or less

extent.

The influence which rapid evaporation from the lungs and skin exerts on our feelings, is very strikingly exemplified in the reports of those who have ascended lofty mountains, or gone up in balloons; they almost always experience thirst, which is sometimes intolerable, even when it cannot be ascribed to the fatigue of exercise; it is only momentarily satisfied by large draughts of drink; but if the air becomes charged with moisture, this most painful symptom is at once relieved; the evaporation is lessened, and absorption goes on actively. The good effects of frequently sponging the skin, during fevers, and also at sea, when the supply of fresh water is scanty, are other proofs of the impotence of the cutaneous functions. Dr. Edwards remarks, that in many experiments in which animals were confined in rarified air, he observed that a disposition to vomit was induced. This accords with what we notice in dyspnoea from other causes. Whenever the respiration is impeded, as in acute or chronic pulmonary congestions, a disposition to vomiting is frequently induced; the community of the nervous supplies of the lungs and stomach may possibly account for this phenomenon. Whenever some persons enter a room, much heated in cold weather, they experience a painful sensation in the chest; this is chiefly attributable to the rapid evaporation from the surface of the air-cells; and the old custom of placing upon the stove a vessel containing water, is warranted by theory, as well as by practice.

We stated that children, who are born prematurely, have a very feeble power of producing heat; hence it becomes an object of great importance in attempting to rear such children, to compensate the deficiency by exter

nal means.

The researches of Dr. Edwards point out to us the importance of the skin as an accessory, and in some degree a vicarious organ of respiration from being unencumbered with hair or feathers, in man, impressions made upon it are much more lively; and in this respect he has the advantage over all warm-blooded animals, even the hibernating; their skin is less accessible to the air; and hence no doubt the reason that an adult can seldom or never

be resuscitated, when all external motion has ceased by drowning. Man, on the contrary, whose skin is bare, delicate, and sensible, may be re-animated by the action of the air, when he appears to have lost under water sense and motion. A great error is frequently committed by medical men in their attempts to restore life, in cases of asphyxia; we have seen how very hurtful a too great and long-continued external heat and a confined respiration are, when the energies of life are faint and low. If momentarily and very suddenly applied, good effects may indeed be obtained; thus, the mere immersion of a new-born child in warm water, is frequently a most efficacious means of re-animating it; but, as soon as signs of returning irritability and feeling are shewn, or if they be very tardy in appearing, we had better desist from a method which, if too much prolonged, may be fatal. If an animal is plunged in water of 104° F. its movements are much more forcible, but less numerous, than at inferior temperatures.

While reflecting upon these remarks of Dr. Edwards, we have been induced to question, in our own minds, the propriety of a long-continued application of external heat, in the form of steam or heated air, in that disease which has so much baffled alike physiological speculation and therapeutic aid. In no member of the nosological catalogue, is there such a remarkable diminution of animal temperature as in cholera; the true explanation of it may be obscure; but we think that most will agree with us in partly, at least, referring it to the state of the blood. We have no intention of indulging farther in speculation, especially as we deem it not improbable that Dr. Edwards himself may have directed his attention to the disease in Paris; certainly no man is so well fitted to elucidate some of its mysteries, In concluding our review of Dr. Edwards' researches, it must appear quite unnecessary to detain our readers with any long-drawn eulogy; we have already expressed our opinion of his high merits; and, after the perusal of the preceding pages, all will be fully enabled to form their own estimate. It has rarely fallen to our lot to analyze any book, containing more original and interesting observations; and, if a feeling of regret can mix itself with the pleasure of our labours, it has been, that a foreign country and a foreign language have had the honour of its parentage. The different sections of the book were presented, in the form of separate papers or essays, to the Royal Academy of Sciences at Paris, and obtained for the author, although a stranger, the honour of the physiological prizes. Would that a similar institution, conducted on similar principles of enlightened liberality, and directed by men of minds as free of the love of pelf, and of the bigotry of obsoletism, arose to add dignity and honor to our native land! But we fear that the heads of the profession, or rather, we should say, the autocrats of our different institutions, are not the beings from whom we can expect such good; and we must trust to that spirit of generous intelligence which begins to animate the great bulk of our medical brethren, for better days and nobler doings. It was acutely observed to us, by one whose high and varied talents may yet make his name revered by the profession, that monarchy may be the best government for a nation, but that, assuredly, it is a republic alone which science and literature can ever acknowledge. No; we can no longer endure the petty thraldom of pride and sycophancy. Shall it be said that in Britain, the land of civil liberty and enlightenment, where the path of distinction is as open to the humblest commoner as to the

proudest noble, a meaner bondage and a more galling despotism exist in the medical legislature, than is to be found at Petersburg or Constantinople? But the time is at hand, and a mighty change is awaiting us-for it has been well observed, that "the moment oppression passes one step beyond endurance, that step takes to liberty." May the day soon come, and may we have our Academy of Sciences, to foster and reward the professional talent of those, who now seek and find it elsewhere. Dr. Edwards probably felt that his labours would be better appreciated, and we may certainly add, more zealously examined, in Paris than in London; be this as it may, he has proved himself one of the most accomplished physiologists of modern times, and we trust that he may yet reap fresh and more distinguished laurels. His present work exhibits the most unwearied industry, and, at the same time, great penetration and ingenuity; he is quite an original thinker, and his mind is evidently stamped with the signet of true philosophy.

The success with which he has examined some of the most obscure phenomena of life, pointing out their association and harmony, and their conexion with some general laws, which seem to pervade and influence the vitality of animals, from the lowest to the highest-the admirable fitness of experiments, the ingenuity of their contrivance, and the skill of their executionthe strict and logical accuracy of most of his inductions, and the practical importance of many, fully warrant our high encomiums. Moreover, in addition to his own immediate discoveries, he has thrown much light on the researches of others, and has been enabled to reconcile most happily, the conflicting and discrepant views of different authors. There is so much sound truth and acute observation in the following passage, that we cannot refrain from directing the reader's attention to it.

"From one being accustomed to find a constancy in the phænomena of inorganic nature, and habituated to judge of the truth of the results of experiment by the possibility of our reproducing them at pleasure, we are led to seek with anxiety for the same character, in an order of facts which are necessarily variable. Hence the difficulty of obtaining general assent to the results of physiological experiments, which by their nature are precluded from offering that uniformity on which the inind reposes with confidence.

Convinced that different and even opposite results do not necessarily exclude each other, when vitality is concerned, I have always endeavoured so to vary my experiments, that I might reproduce some of the phænomena which appear contradictory in the works of other physiologists." 226.

To Dr. Hodgkin great praise is due, for the manner in which he has executed his task; but he might have rendered the work more saleable, and, therefore, more generally useful, had he shorn it of some extraneous matter. To introduce an inaugural thesis, and a juvenile essay, savours rather too much of what, in parliamentary language, is termed "adding a rider to a money bill," by which the Commons, as is well known, frequently manage o obtain the sanction of the Lords and King to a measure, by affixing it to any grant of supplies; and we regret it the more, because it has prevented him, we are told, from publishing the copious tables of Dr. Edwards, appended to each section, and in which the individual results of the very numerous experiments, and the conclusions to be drawn from them, were specially detailed. Surely the acquisition of these would have been more valuable than a Latin thesis on Absorption, various essays, on Atmospheric