the last permanent tooth is formed before the temporary ones are shed. We shall add the following obervations without a remark.

In the human species, the mode of dentition is upon the same principle as in the wild boar; only the last-formed grinding teeth in each jaw, called dentes sapientiæ, from the late period of life at which they cut the gum, do not in size exceed the others, but are rather smaller, and very often have not sufficient room in the jaw to come into their regular place, although they do not make their appearance till between twenty and thirty years of age.

In the negro, the dentes sapientia have sufficient room to come into their place, and are in general full as large as the other grinders; the growth of the posterior part of the jaw being evidently greater than in the European.

When the age of man was much greater than at present, it is natural to suppose the growth of the posterior part of the jaw was continued for a longer time, and the space for the dentes sapientiæ was more extensive. Under such circumstances, these teeth would probably be large, in proportion to the space which was to receive them; and when, instead of threescore and ten, a thousand years was the period of a man's life, we should be led to conclude, from the preceding observations, that there was a succession of dentes sapientiæ.

There is a very curious circumstance in favour of this conjecture, which has been mentioned to me by Sir Joseph Banks. In Otaheite, the natives have a tradition, that Adam, or the first man, was remarkable for the length of his jaws. His name, in their language, is Taa roa tabi etoomoo, which signifies the one (the stock) from which all others sprung, with the long jaws; so that these islanders have a tradition of the original race of men having had their jaws much longer than at present.' P. 323.

The teeth of the animal incognitum, found on the banks of Ohio in North America, appear to be constructed on the same principle. This is also a long-lived animal, though it be by no means certain that it has tusks. The boar, our author supposes, must be long lived, from its vast bulk often described, and the terror which, at different periods, it has excited.

• XV. Account of some Experiments on the Ascent of the Sap in Trees. In a Letter from Thomas Andrew Knight, Esq. to the Right Hon. Sir Joseph Banks, Bart. K.B. P.R.Š.'

We find it very difficult to understand these experiments, without some better assistance from, or a more minute reference to, the plates. The author seems to have shown, that the nutrition of the bark is from the descending sap, derived from the leaf; and the whole action of each leaf appears to lie between itself and the root. The medulla is by no means necessary to the progress of the sap; and the leaf will perform its office without the aid of this central portion. The following observations merit our attention.

Whilst I was waiting the result of the preceding experiments, I made a few efforts to discover another branch of circulation, namely, that which takes place within the fruit, and conveys nourishment to the future offspring. My experiments were here, however, confined almost entirely to two species of fruit, the apple and the pear; and, therefore, as the organisation of different fruits is evidently different, I do not consider my observations such as can throw much general light on the subject. Examining the fruit-stalks of the apple, the pear, the vine, and some other fruit-trees, I found their organisation to be nearly similar to that of the branch from which they sprang, and to consist of the medulla, the central tubes, a very small portion of wood, the spiral tubes and those of the bark, and the two exter. nal skins. Tracing the progress of these in the full-grown fruits of the apple and pear, I found, as Linnæus has described, that the medulla appeared to end in the pistilla. The central vessels diverged round the core, and, approaching each other again in the eye of the fruit, seemed to end in ten points at the base of the stamina, to which I believe they give existence. The spiral tubes, which are in all other parts appendages to these vessels, I could not trace beyond the commencement of the core; but, as the vessels themselves extend through the whole fruit, it is probable that the spiral tubes may have escaped my observation., Linnæus supposes the stamina to arise from the wood. I should not venture to state an opinion in opposition to his; but I believe he has not any where distinguished those I call the central vessels, from the common tubes of the wood.

Having hitherto found that all advancing fluids appeared to pass either along the tubes of the alburnum, or along the central vessels, I had little doubt that the fruit was fed through the latter; but my efforts to ascertain this, in the autumn of 1799, were not successful. In the last spring I was more fortunate. Placing small branches of the apple, the pear, and the vine, with blossoms not yet expanded, in a decoction of logwood, I found that the colouring matter readily passed up the central tubes of the fruit-stalks of ail; and, in the apple and pear, I easily traced it, through the future fruit, to the base of the stamina. The office of the tubes in the bark did not appear in this experiment; but, as I have reason to believe the motion of the sap in the bark to be always retrograde, I am disposed to conclude that it is so here, and that, through the bark of the stalk, any superfluous humour existing in the fruit, from excessive humidity of weather, or other cause, is carried back and absorbed by the tree. I have, however, very frequently repeated an experiment on the vine, which, I think, evidently proves that the fluid returned (if any) is essentially different from that which is derived from the leaf. In the culture of this fruit, I have frequently pinched off the young shoot, immediately above a bunch, as soon as the latter became visible in the spring, letting the leaf opposite the bunch remain. In this case, the wood below the upper leaf acquired nearly its proper length and substance. But when I have taken off that leaf, the wood between the bunch and the next leaf below has ceased to elongate, and has remained, in form and substace, similar to the small fruit-stalk attached to it. P. 339.

The fruit of apples and pears is nourished by central vessels; and the internal organisation appears, to our author, to resemble that of the placenta and umbilical cord in the human system. In considering the cause of the ascent of the sap, Mr. Knight rests on the irritability of the vegetable, and transfers to vegetation the doctrine of accumulated and exhausted irritability. His own instance of the peach-tree, at the end of p. 343, is, we think, decisive against it; for the irritability must have been here exhausted. The silver grain, as it is called, diverging from the medulla to the bark, are, it is said, the agents of the propulsion of the sap, and these are affected very powerfully by heat and moisture, even after the tree is sawed into planks. Our author's arguments and observations in support of this idea must be read in the paper; for they would detain us too long, were we to attempt an abstract of them. The medulla Mr. Knight thinks to be a reservoir of moisture; and the heart of the wood, distinguished from the alburnum, is designed, in his opinion, to supply the place of bone.

• As I have not been able to find the spiral tubes any where, except immediately surrounding the medulla in different parts, in the seed, and in the leaf, and as they every where terminate at short die stances, I conclude that the sap is not raised by their agency, nor by the central vessels, to which they are appendages; for these extend no greater length downwards than the spiral tubes, and termi nate with them, at the external surface of that annual layer of wood to which they belong; and they have not any apparent communica tion with the similar vessels of the succeeding year. In the lower parts is of hollow trees they must long have ceased to exist at all; and in all trees, except very young ones, they are (as it were) ossified within the heart-wood; and those in the annual shoots and buds are often a hundred and fifty feet distant from the roots, from which they are supposed to raise the sap.

The common tubes of the alburnum (which do not appear to me to have been properly distinguished from the central vessels by the authors that I have read) extend from the points of the annual; shoots to the extremities of the roots; and up these tubes the sap most certainly ascends, impelled, I believe, by the agency of the silver grain. At the base of the buds, and in the soft and succulent part of the annual shoot, the alburnum, with the silver grain, ceases to act and to exist; and here, I believe, commences the action of the central vessels, with their appendages, the spiral tubes. By these the' sap is carried into the leaves, and exposed to the air and light; and here it seems to acquire (by what means I shall not attempt to decide). the power to generate the various inflammable substances that are found in the plant. It appears to be then brought back agam, through the vessels of the leaf stalk, to the bark, and by that to be' conveyed to every part of the tree, to add new matter, and to compose its various organs for the succeeding season. When I have in-,

tentionally shaded the leaves, I have found that the quantity of alburnum deposited has been extremely small.' P. 351.

'XVII. On an improved reflecting Circle. By Joseph de Mendoza Rios, Esq. F.R.S.'

Of this improvement it is impossible to convey an intelligible description.

• XVIII. Observations and Experiments upon Dr. James's Powder; with a Method of preparing, in the humid Way, a similar Substance. By Richard Chenevix, Esq. F. R. S. M. R. I. A.'

The antimonial powder is well known to be a very uncertain preparation of antimony; and few, we believe, with every precaution, can produce it in two different processes of equal strength. Fire, as Mr. Chenevix properly observes, is too precarious and uncertain an agent. It is highly probable that there is no chemical combination of the antimony and the phosphoric acid in this preparation. In the humid way the same ambiguity exists; but the strength of the preparation is more uniform, though the medicine be less active. We shall add the process.

Dissolve, together or separately, in the least possible portion of muriatic acid, equal parts of the fore-mentioned white oxyd of antimony and phosphat of lime*. Pour this solution gradually into distilled water, previously alkalizated by a sufficient quantity of ammonia. A white and abundant precipitate will take place, which, well washed and dried, is the substitute I propose for Dr. James's powder.' P. 379.

Some satisfactory evidence is added of the similarity of the effects of this powder with those of the common antimonial powder, allowing for its weaker power.

XIX. Case of a young Gentleman who recovered his Sight when seven Years of Age, after having been deprived of it by Cataracts before he was a Year old; with Remarks. By Mr. James Ware, Surgeon. Communicated by Maxwell Ġarthshore, M.D. F.R.S.'

We must suppose that the young man had seen objects in

In order to procure the phosphat of lime, I dissolved in muriatic acid a quantity of calcined bone, and precipitated by ammonia, in its state of greatest causticity. By this means the excess of muriatic acid, which held in solution the phosphat of lime, is saturated, and the phosphat is precipitated; but no muriat of lime is decomposed, if the ammonia is quite free from carbonic acid. This is the most direct method of obtaining phosphat of lime pure. This salt is not decomposed, as some have asserted, by muriatic acid, but merely dissolved by it. I have been induced to state fully the particulars, because, from the beneficial effects of this salt in the treatment of rachitis, as proposed by M. Bonhomme, (Annales de Chymie, vol. XVIII. p. 113,) it may become of general use. The oxyd of antimony I obtained by precipitating, by water, the common butter of antimony of the shops.'

some imperfect degree, or that Mr. Cheselden's narrative is fa bulous. Yet we recollect discovering, among the papers of an old surgeon, a MS. of a similar case; and we recognise no great difference in the representation from that of Mr. Cheselden. We therefore suspect that the same sense which could distinguish colours could give the idea of distance. We shall select the author's recapitulation of the whole paper.

First, When children are born blind, in consequence of having cataracts in their eyes, they are never so totally deprived of sight as not to be able to distinguish colours; and, though they cannot see the figure of an object, nor even its colour, unless it be placed with in a very short distance, they nevertheless can tell whether, when within this distance, it be brought nearer to, or carried farther from them.

Secondly, In consequence of this power, whilst in a state of comparative blindness, children who have their cataracts removed; are enabled, immediately on the acquisition of sight, to form some judgement of the distance, and even of the outline, of those strongly defined objects with the colour of which they were previously ac quainted.

Thirdly, When children have been born with cataracts, the crystalline humour has generally, if not always, been found either in a soft or fluid state. If, therefore, it be not accompanied with an opacity, either in the anterior or posterior portion of the capsule, and this capsule be largely punctured with the couching needle, introduced in the way in which this instrument is usually employed to depress the cataract, there is reason to expect that the opaque matter will, sooner or later, be absorbed, the pupil become clear, and the sight be restored.

Fourthly, If, in addition to the opacity of the crystalline hu mour, its capsule be also opaque, either in its anterior or posterior portion, or in both, (which circumstance cannot be ascertained be fore the operation,) and, in consequence of this, the operation above mentioned should not prove successful, it will not preclude the performance of extraction afterwards, if this be thought adviseable.

Fifthly, The operation above mentioned being much more easy to perform than that of extraction, and it being possible to fix the eye with perfect safety during its performance, by means of a spe culum oculi, it may be undertaken at a much earlier age than the latter operation; and a chance may of course be given to the patient of receiving instruction, without that loss of time which has usually been thought unavoidable, when children are born with this disor der.' . 394.

• XX. An Account of some Galvanic Combinations, formed by the Arrangement of single metallic Plates and Fluids, analogous to the new Galvanic Apparatus of Mr. Volta. By Mr. Humphry Davy, Lecturer on Chemistry in the Royal InCRIT. REV. Vol. 34. March, 1802.

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