obtaining the acid free from water but it seemed impossible to accomplish this point, without uniting it to some other substance, which made it equally unfit for the purpose of experiment. The results that were obtained, though not decisive, render it probable that the base of the muriatic acid is a substance of great inflammability; and from analogy we may conjecture that it is of a metallic nature. The author concludes by observing that

The facts advanced in this lecture, afford no new arguments in favour of an idea to which I referred in my last communication to the Society, that of hydrogen being a common principle in all inflammable bodies; and except in instances which are still under investigation, and concerning which no precise conclusions can as yet be drawn, the generalization of Lavoisier happily applies to the explanation of all the new phenomena.'

It gives us the greatest satisfaction to learn that Mr. Davy is still ardently pursuing his researches in the field of discovery, into which he has advanced with such unexampled

success.

A Letter on a Canal in the Medulla Spinalis of some Quadrupeds. In a letter from Mr. William Sewell to Everard Home, Esq. F.R.S-We have here an account of a canal which extends from the calamus scriptorius, the apparent termination of one of the ventricles of the brain, along the centre of the spinal marrow. It was found in the horse, the bullock, the sheep, the hog, and the dog; it appears to be an uninterrupted tube during its whole length; and it contains the same kind of fluid that exists in the ventricles of the brain.

A numerical Table of elective Attractions; with Remarks on the Sequences of double Decompositions. By Thomas Young, M.D. &c. The author here remarks that several efforts have been made to form a series of numbers, which may represent the mutual attractive force of the component parts of different salts, but that the attempts have hitherto all proved imperfect. The convenience which would result from our being in possession of such a table is sufficiently obvious, since by the help of it nearly all the phenomena of the mutual actions. of a hundred different salts may be correctly represented by a hundred numbers, while, in the usual manner of relating every case as a different experiment, above two thousand separate articles would be required.' Dr. Young informs us that he has succeeded in constructing this series of numbers; which, though they may not be an accurate measure of the forces, yet approximate to accuracy, and may afford a proportional standard

A a 4

standard which to each other.

may

shew the relation of the different bodies

As the basis of his arrangement, Dr. Y. lays down the principle that the attractive force which unites two bodies may be always denoted by a certain constant quantity; whence he infers that a regular gradation must exist in the simple elective attractions; together with an agreement between the simple and the double attractions, and a continued sequence in the order of the double elective attractions. As to the correctness of the tables, we do not undertake to offer any opinion; only remarking that the acknowleged talents of the author would incline us to place confidence in whatever is given under his authority.

Account of the Dissection of a human Fetus, in which the Circulation of the Blood was carried on without a Heart. By Mr. B. C. Brodie.-This is the case to which we referred in our account of Dr. Young's paper, (p. 355.) of a foetus of considerable size, in which the heart was entirely wanting. The subject was one of twins who were born dead; and it had all the external parts of the body, although several of them were marked by some deficiencies. On opening the thorax, the following appearances were observed:

In the thorax there was no heart, thymus gland, or pleura. The trachea was situated immediately behind the sternum. It had its natural appearance, and divided as usual into the two bronchia. The latter terminated in the lungs, which consisted of two rounded bodies, not more than one third of an inch in diameter, having a smooth external surface, and composed internally of a dense cellular substance. The esophagus had the usual situation, but it terminated in a cul de sac at the lower part of the thorax. The rest of the thorax was filled with a dense cellular substance; and in place of the diaphragm, there was a membranous septum between it and the cavity of the abdomen.'

In the abdomen, the peculiarities were that the stomach had no cardiac opening, the colon had not its appropriate structure, and there were no omentum, liver, nor gall-bladder. The umbilical chord consisted of the vein and only one artery; it entered in the usual part; and the artery was carried down by the side of the urachus to the left groin.

Here it gave off the external and internal iliac arteries of the left side, and was then continued upwards on the fore-part of the spine forming the aorta. From the aorta arose the common trunk of the right iliac artery, and the branches to the viscera and parietes of the thorax and abdomen. At the upper part of the thorax, it scut off the two subclavian, and afterwards divided into the two carotid arteries, without forming an arch. The veins corresponding to these arteries terminated in the vena cava, which was situated on the anterior

terior part of the spine before the aorta, and passed downwards before the right kidney to the right groin. Here it became reflected upwards by the side of the urachus to the navel, and was continued into the larger vessel or vein of the chord.'

It appears, therefore, that this foetus not only had no heart, but no communication between the trunks of the arteries and veins; so that they were united merely by their extremities, either in the placenta or in the foetus. The blood must consequently have been propelled along the whole course of the circulation by the action of the vessels, and probably of the arteries; and it follows from this distribution of the sanguiferous system, that the whole of the blood must have passed through the placenta at each circuit. We think that the

remark of Mr. Brodie is incorrect, when he says that the placenta must have been at once the source and the termination of the circulation: it can no more be considered as the termination than the capillary vessels in the foetus; and we conceive that the source of the circulation must have been derived from the arteries. We regret that nothing is said about their structure; which, it may be conjectured, would have exhibited an unusual degree of muscularity, because we generally find that, when any deviation from the ordinary structure of the body prevails, some other organ is furnished with such additional powers as may enable it to become a proper substitute for the defective parts. It is a circumstance worthy of notice that, in all those cases in which no heart has been formed, the liver also has been wanting.

On the Origin and Formation of Roots. In a Letter from T. A. Knight, Esq. E.R.S. to Sir Joseph Banks.-In one of his former papers on vegetable physiology, Mr. Knight endeavoured to prove that the buds of trees always spring from the alburnum, and he informs us that to this opinion he still finds reason to adhere. The object of the present communication is to shew, that the roots of trees are always generated by the vessels which pass from the cotyledons of the seed, and from the leaves, through the leaf-stalks and the bark, and that they never, under any circumstances, spring immediately from the alburnum.' It has always been supposed that the radicle of the seed is the rudiment of the future root of the plant: but Mr. K. proposes to shew that this opinion is erroneous. had before pointed out a circumstance which appeared to be essential to the formation of a proper root, viz. that it is always lengthened by the addition of successive new parts to its apex, whereas the shoots increase by the extension of parts previqusly organized. Now, in the case of the radicle, it appears

He

that

that it grows by extension, and is therefore not analogous to a proper root. This part, Mr. Knight imagines, comes into existence during the germination of the seed, and springs from the point of the radicle: but at this period the alburnum is not yet formed; while, on the other hand, the cortical vessels are full of sap, and are therefore well fitted for producing the true root. It is also found that the leaf-stalks of many plants possess the power of generating roots, though they never contain any portion of alburnum. If the shoots of a vine be divided, so as entirely to prevent the passage of the sap, roots are readily formed from it, and they always proceed from the upper lip of the wound only. It seems clear that they are generated by the sap which descends through the

cortical vessels.

Mr. K. then notices the fact that the same part of a plant may be made to form either buds or roots; not that they are convertible into each other, but that the alburnum is better fitted for carrying its sap upwards, and thus, under favourable circumstances, for producing buds, while the cortical vessels permit their fluids to move in an opposite direction. It is not easy to decide whether the fluids, which move in these opposite directions, be similar: but Mr. Knight suspects that they are; and he seems to conceive that the mere circumstance of the fluid moving in one case upwards, and in the other downwards, will account for its producing either buds or roots. He informs us that he has been investigating the cause which directs the roots of plants in search of their proper nutriment, and proposes to make it the subject of a future communication: it is a very interesting inquiry; and we are gratified by hearing that it has engaged the attention of so able an experimentalist.

On the Nature of the intervertebral Substance in Fish and Quadrupeds. By Everard Home, Esq. F.R.S. During an examination of the squalus maximus, Mr. Home found that, when the intervertebral subtance was cut, a fluid rushed out of it with great force. The cavities which contain it are each capable of holding about three pints; their sides are ligamentous and elastic; and when they are emptied of their contents, the vertebræ are brought considerably nearer to cach other. The magnitude of the parts enabled Mr. Home to examine the peculiar mechanism of the joints to great advantage, and he afterward extended his researches to the vertebræ of other animals. The mechanism itself appears to be extremely beautiful, and Mr. Home's account of it is ingenious:

The

The fluid contained in the cavity being incompressible, preserves a proper interval between the vertebræ to allow of the play of the lateral elastic ligaments, and forms a ball round which the concave surfaces of the vertebræ are moved, and readily adapts itself to every change which takes place in the form of the cavity.

The elasticity of the ligaments, by its constant action, renders the joint always firm independent of any other support, and keeps the ends of the vertebræ opposed to each other, so that the whole spine is preserved in a straight line, unless it is acted on by muscles or some other power. When a muscular force is applied to one side of the spine, it stretches the elastic ligament on the opposite side of the joint, and as soon as that force ceases to act, the joint returns to the former state. This is one of the most beautiful instances in nature of elasticity being employed as a substitute for muscular action.

The extent of the motion in each particular joint is undoubtedly small, but this is compensated by their number, and the elasticity of the vertebra themselves.'

Most kinds of fish seem to possess a structure similar to that which is here described, though the shape of the cavity varies in different species. It is, as the author observes, probably contrived for producing those quick lateral motions of the spine which take place in swimming. The intervertebral substance of the whale is considerably different:

The external portion is very firm and compact, is ranged in concentric circles with transverse fibres uniting the layers together, it becomes softer towards the middle, and in the centre there is a pliant soft substance without elasticity, but admitting of extension more like a jelly than an organized body, corresponding in its use to the incompressible fluid in the fish.'

Several animals were then examined; and the hog and the rabbit were found to approach to the structure of fish in general: but in some other animals, and in the human subject, the form of the intervertebral substance was more similar to that of the whale. The author draws a practical conclusion from these observations, respecting the treatment of the curvature of the spine in young persons, especially females; and he observes that it must be extremely prejudical to stretch the intervertebral ligaments, since in that case the intervertebral substance must be unable to support the bones in their proper position.To the paper is appended a chemical analysis of the fluid by Mr. Brande, from which he infers that it consists of mucus.

MECHANICS.

An Account of a Method of dividing Astronomical and other Instruments, by ocular Inspection in which the usual Tools for graduating are not employed; the whole Operation being so contrived, that no Error can occur but what is chargeable to Vision, when assisted