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perhaps, is not yet sufficiently advanced to enable us to assiga the true reason of this deviation from the usual proportions in expired air; but it is evidently connected with the unnatural circumstances of the experiment, and probably with the distress suffered by the operator, and the consequent diminution or loss of voluntary power. Messrs. Allen and Pepys have concluded it to arise from absorption of oxygene under such circumstances; but this opinion Mr. Ellis justly observes is not only opposed to the physiological considerations already noticed, but also to the fact that in experiments approximating most nearly to natural respiration, the diminution is too inconsiderable and too unsteady to be owing to any other than accidental causes. Besides, in one of their own experiments there was not only no diminution whatever, but an actual increase of ll cubic inches in the volume of expired air. With respect to the exact correspondence between the formation of carbonic acid, and disappearance of oxygene in natural respiration, observed in the experiments of these gentlemen, it may be remarked that Mr. Dalton satisfied himselî of the same fact by repeated experiments; and Dr. Menzies, in the course of his examination, found the volumes of inspired and expired air to correspond most accurately.

It appears therefore from an impartial estimate of all the data in our possession, to be a strictly legitimate inference, that in natural respiration, the volume of air expired is equal to the volume inspired, and that the carbonic acid contained in the expired air corresponds exactly in volume with the diminution of oxygene which the air is found to have sustained in passing through the lungs; but that when the respiratory function is oppressed by the frequent respiration of the same air, irregularities take place which render the experiments perfectly inconclusive. With respect to the nitrogene which constitutes so large a proportion of atmospheric air, notwithstanding the conclusions which Sir H. Davy has drawn from his experiments on the respiration of nitrous oxide, in favour of its being absorbed by the blood, as well as the opinions of others who have adopted that view of the subject, still it is evident from the examination which Mr. Ellis has given the question, that it is totally destitute of any positive proof, and is opposed by considerations of insuperable difficulty. Not only is the idea of air passing into the blood through the cells of the lungs entirely gratuitous, but as far as nitrogene is concerned it has no affi nity whatever for the blood; and any other elastic fluid, hydrogene for example, may be substituted for it without inconvenience to the animals,-facts which, added to the pretty exact correspondence of volume in the expired and inspired air, are

quite conélosive against its being absorbed, of exerting any degree of active agency in the process of respiration.

It has rarely happened, however, that philosophers have been satisfied to linit their conclusions within the precise boundaries of their own experience and observation, and hence we so frequently find a certain portion of hypothesis engrafted upon truths, the certainty of which has been placed beyond the range of doabt. The notion of a chemical combination taking place in the lungs between the blood and the air, has been consequently supposed to receive confirmation, not merely from the diminution of volume which has been already adverted to, but also from the constant formation of carbonic air during respiration. To explain this fact it has been asserted that the oxygene of the atinosphere is absorbed by and enters into combination with thie venous blood as it circulates through the lungs ; the formation of carbonic acid being either an immediate result of this combination, or else taking place indirectly during the circulation of the blood through the body subsequent to its oxygenation, and being finally evolved on the return of the blood to the lungs. This hypothesis has received its principal support from the change which served to undergo in its circular: e venous blood has been ob

the lungs. About the middle of the seventeenth century it was first observed, that the upper surface of venous blood received into a vessel, acquired a scarlet colour from exposure to the air, and that if the surface was removed, the recently exposed surface speedily acquired the same florid hue, so that by repeating this successively, the whole might be made to undergo this change of colour. Now the blood in its circulation through the lungs undergoes a change precisely similar. It is conveyed thither from the right side of the heart of a dark red colour, approaching to black, and afterwards is returned to the left side of the heart of a bright Horid red colour. In the former state it is venous, in the latter arterial blood. And this change has been effected, notwithstanding the interposition of the membrane forming the air cells, and the coats of the vessels, by the agency of the atmospheric air, which is constantly supplied by the act of respiration.

That this change of colour is connected in some way or other with the presence and agency of oxygene is proved by numerous facts. . It takes place only when that gas is présent : pure oxygene produces a greater effect than atmospheric air; nor is the change prevented by covering the crassamentum with serum or some other animal fluids, though it does not take place when a coating of oil or water, or other similar substances is interposed.: Dr. Priestley, however, discovered that Fenous blood exposed to the air in a bladder, had the surface Vol. X.

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in contact with the bladder changed to the florid colour of arterial blood ; and upon this fact considerable reliance has been placed as evidence of the absorption of oxygene in the lungs, since in this case also a dense animal membrane is interposed between the air and the blood. Mr. Ellis, we think, has proved by satisfactory experiments, that the fact itself will not admit this inference. Whenever blood is placed in contact with air, together with this change of colour, there is a formation of carbonic acid, but no diminution of volume in the air. It is ascertained, too, that if a bladder containing blood is suspended in a vessel of air, precisely similar changes take place; the oxygene being converted into carbonic acid, but without

any

loss of volume. And a further pursuit of the subject has shewn that precisely the same effect is produced on the air, if the bladder is filled with water, or placed in the jar merely moistened with water. This effect on the air is indeed produced generally by moist animal substances, and the effect on the colour of the blood is probably a consequence only of the combination of the oxygene with carbon.

When this curious subject shall have been more completely investigated, it may possibly be found to stand connected with some reciprocal changes in the electrical state of the different agents concerned in the process of respiration. We know that air which has been respired is in a negative state, while the surrounding atmosphere is positive ; nor is it improbable, as Mr. Ellis has suggested, that the condensation of the air, which certainly takes place in the lungs on some occasions, may be connected, in some degree, with the agency of this subtile fluid. If, then, we have not only no positive proof of the oxygene entering into immediate combination with the blood in its circulation through the lungs, but also evidence almost demonstrative that such an union cannot happen, we must conclude that the formation of carbonic acid takes place in the «ells of the lungs, and that the union of the oxygene with carbon must take place exterior to the vessels which contain the circulating fluids. The carbon therefore which is removed by the respiratory function of animals must be considered as an animal exçretion dependent, as other processes of that nature are, on the activity of the circulation, and consequently evolved by the living functions of the animal. In what precise state the carbon may be given out by the exhalent vessels we know not : but Mr. E. has proved by a copious induction of facts, that the quantity is regulated in a great degree by the vigour with which the functions of the animal are performed, and that when they are diminished or suspended by very low degrees of temperature, it is greatly diminished or ceases entirely. The excretory functions of the lungs of animals and the leaves of plants must

be considered therefore as the immediate source of the carbon which is removed by the air with which it enters into combination, but its more remote source must be sought in the means which all animated beings possess of supplying the waste of their fluids, by a constant addition of matter to that fluid from whence all the secretions are derived, and the health and activity of the system maintained.

The conclusion to which Mr. Ellis has been conducted by the extensive range of investigation which he has embraced in these volumes, may be comprised, he observes ' nearly, in this simple statement : that oxygene gas is uniformly converted into carbonic acid during the exercise of the respiratory function, and that by this chemical change in the air, its latent or specific caloric is set free, and enters into the vegetable and animal systems.' -Our limits do not allow us at present to enter into the consideration of the latter portion of this conclusion which relates to the source of animal temperature, but notwithstanding the attempts which have been made recently to overturn the theory which Mr. E. has embraced, we cannot help regarding it as the only satisfactory one which has yet been proposed, and resting on too firm a foundation of experiments and induction to be lightly abandoneda

Art. XIV. Sermons on Various Subjects : By John Styles. 8vo. pp.

430. Price 10s. 6d. Williams, and Co. 1813. VIGOROUS freedom, and sometimes impressive originality

of thought-variety and vivacity of appropriate illustration enlightened warmth and tenderness of heart in delineating the sufferings and sorrows of human life, and in administering suitable instructions and consolations --- peculiar fervency of appeal to the intellect, the conscience, and the passions, in favour of the love and practice of whatever is humane, and moral, and devout--and an elevated abhorrence and indignant reprehension both of the wiles and iniseries of infidelity, and of the meanness, malignity, and injustice of intoJerance-exhibited in language generally correct and forcible ; these are, in our estimation, among the most prominent distinctions of this interesting volume.

Yet with these excellencies, it must in propriety be owned, that Mr. Styles has suffered several imperfections to intermingle. The work bears numerous traces of haste and negligence, and a forgetfulness of some essential dictates of a refined literary taste, while various other passages are evidently over laboured. We have to complain, too, of an occasional obscurity, inflation, and undue vehemence of expression ;

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and notice a neglect of proportion in the different branches of some of the discourses, not little injurious to the pleasing effect which the mind always feels to result from the regular symmetry of composition; and which, though a fault not easily avoidable in the fervoar of extempore writing, is yet always to be corrected in the cooler : hours of deliberate revision. The frequent quotations which the author has made from prose writers in these sermons, though mostly good in themselves, seem too frequently re-i sorted to as the resource of temporary indolence, and really impair the interest and unity of the composure. Nearly the whole of these should be expunged. And as for the many poetical citations which likewise overspread the volume, we are frankly of opinion, that they form a species and quantity of ornament quite unworthy of the manly writer who has condescended to employ them. He seems himself aware of some of the objections which they are calculated to provoke in serious minds, and attempts an apology for their in-' troduction in the preface : but his excuses, in our opinion, are neither forcible nor apposite. We proceed, however, to the more agreeable employment of exhibiting to our readers a few of those passages in which Mr. Styles's powers appear to have been exerted with the happiest effect.

We may take our first quotation from the close of the first sermon, entitled " Christianity the Friend and Promoter of Social Happiness, a powerful and animated representation, of the progressive beneficial effects of this most holy and blessed system. Mr. Styles is rejoicing in the efforts which are making to enlighten the lower orders of our population :

• When the population of a country is taught to enquire, to investigate, and to compare, the most important results may be expected to take place. When ignorance retires, and prejudice is vanquished; when the aid of reason is sought, and its dictates obeyed, the state of society must necessarily improve ; and it may be laid down as a fundamental principle, established by the experience of all ages and nations, that religious knowledge is the parent and patron of all useful science. Besides this, it promotes as far as its powers extends, the stability of kingdoms. This it does, by surrounding governments with a kind of omnipresent example of virtue, by which it powerfully checks that disposition to enslave and oppress, which so naturally aceompanies the possession of authority; and by attracting the blessing and protection of providence. A corrupt, overbearing, and tyrannical government, carries in its own busom the seeds of destruction. Virtue is the only solid basis of power, and in proportion to the virtue of its public priociples and conduct, is the real prosperity of a nation. If ever vice preponderates in the councils and measures of a government, either in its foreign or domestic policy, its ruin cannot be far distant. But power has a direct tendency to mis

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