meeting with them, it issues into the mine with a considerable velocity. These gas-yielding rents are frequently met with in the coal-mines round Newcastle-on-the-Tyne; and the gas is often discharged into these mines in such streams, as to be compared, in force and quantity, with the air from powerful blast furnaces; but the quantity of gas discharged, however great at first, continually decreases till the rents cease to yield it.

The gas-yielding parts of the coal differ considerably in dimensions; they are situated at variable distances from one another; and the quantity of gas varies very much in different parts, as well as in different situations in any one part. Sometimes the gas-yielding" parts have the characteristic appearance of the common coal, but occasionally they are softer, in small pieces, or dusty; in some parts iron pyrites is abundant; in others it is not found; water sometimes enters the mine along with the gas, but often the gas comes off alone; but the coal has its characteristic appearance, or is soft, in small pieces, or dusty, in many parts which give out water, but not gas; so that the parts which produce this gas, appurently, are not essentially different to those which do not produce it.

When the carbureted hydrogen gas leaves the coal alone, it comes off silently; but when accompanied with water, it always makes a noise. When it enters the mine, along with water, from many pores, in small quantities, and at intervals, various sounds are produced, which have some resemblance to those expertly made on the musical glasses, but which are not so loud, though more agreeable. If the gas escape much quicker, the sounds are considerably lower, but not so various as in the first instance: this is a simmering noise, and would be well imitated by the noise from the pipes of a few tea-kettles when boiling gently. But if the gas escape more copiously than in the last instance, it makes a hissing noise, not unlike, but not so loud, as that made by the steam escaping quickly from the safety valve of a steam-engine.

If the gas is set on fire as it enters a working, when the atmospheric current is traversing the mine, its inflammation is carried on, close to the sides of the coal wall, under different circumstances. Where the gas enters the mine sparingly, but from many pores and seams, to set it on fire, the candle must be moved in every direction along the sides or forehead of a working; then it will inflame the gas issuing from one pore, after it has done so with that from another as it moves forwards; and each inflammation will resemble in sound and appearance that which is produced by the firing of two or three grains of gunpowder. When it enters more abundantly after the gas from one pore is fired, the burning gas fires the gas from many other pores, during which the flame flies from the first pore in a very varying direction, and in a very fantastic and entertaining manner; for sometimes it runs horizontally for a small distance, then bends obliquely in different directions, then perhaps horizontally, and then obliquely again, till it ceases. During these

motions the flame of the gas issuing into the mine from the first pore touched the gas from an adjoining pore, and set it on fire, which did so with the gas from a third pore, and thus the motion of the flame continued; but as the gas issues from every pore at intervals, the portion set on fire at the first pore was consumed before another issued from it, but not before it inflamed the portion of gas then escaping from the second pore, which, though consumed before another portion left that pore, communicated with the gas of a third pore, and so on. In this manner the flame's flitting motion was produced. When the gas escapes from the pores of the coal in constant streams, or at least in a succession of portions at very small intervals, the flame is stationary at every pore.

With the help of these remarks, we may make the following conclusions as to the origin of the carbureted hydrogen gas of coalmines. It is a part of the matter of the coaly strata; but how it is separated we cannot exactly determine. It may be set at liberty by the action of the component parts of the coal on one another; but not in the way of decomposition by fermentation. Or it may consist of an original redundancy of volatile matter which has been kept in by pressure, but which, as soon as hollows are made into the coal, is suffered to escape. The gas, by either mode of formation, may very well exist in the rents above the coal: for as these rents were forming, room was made for the gas to lodge in; and, to account for its degree of compression, we know that it afterwards escapes from the coal with a great force, and, if suffered to fill hollows like these rents, would leave them with a similar velocity.

ARTICLE III.

On the Connexion between the Vascular and Extra Vascular Parts of Animals. By Anthony Carlisle, Esq. F.R.S.

(To Dr. Thomson.)

SIR,

Soho square, July 3, 1815. THE following memoir having been partially made known to the public, I beg you to lay it before your scientific readers, as a means of preventing misrepresentation or piracy.

Sir, your obedient servant,

ANTHONY CARLISLE.

General or comparative anatomy, the great branch of natural knowledge on which the rationale of the medical art is founded, has lately risen in esteem, and is every day more accurately and more extensively cultivated. Considering how intimately the discovery of new facts, their relation to each other, and the physiological in

ferences to be drawn from them, are connected with the previous establishment of definite views, of clear intelligible terms, and of strict physical methods; and feeling the importance of the present subject, I hasten to submit this memoir to competent judges.

I am aware that premature generalizations of facts, as well as premature inductions from them, are seldom useful; and I should not have troubled the scientific inquirer with this communication, had I not felt assured that the present state both of anatomy and physiology would authorise it. In my statements I shall purposely avoid all metaphysical pretension to dive into the hidden mystery of vitality, confessing myself wholly incompetent to reduce that within the rules of physical science: a power which appears to my judgment as allied to the nature of an inscrutable First Cause, or as an emanation from it.

power

The vast variety in the substances, texture, bulk, and combinations, which the living animal and vegetable kingdoms exhibit, renders it difficult to define the essential residence of life as connected with any of the modes of organic structure. Some of the compounds and textures of animals are known to be more important for the maintenance of life than others, as the cerebral substancè and the muscular textures; but there is a numerous tribe of living bodies that appear to be wholly destitute of those peculiar parts, of which the entire vegetable kingdom may be adduced as an instance. Habits of meditation and research have led me to conclude that some benefit may arise to physiology from more accurate discriminations between the several substances of living bodies; especially as to the relative dominion of vitality, or of physical causes on those substances respectively.

The active phenomena of life appear to be generally distinct from those of physical causation ; but the passive condition of living substances is not so obvious. The suspended actions of torpid animals and vegetables, and the latent vitality of many of the more simply constructed animals and vegetables during the absence of heat and moisture, show the intimate connections which subsist between vitality and physical causes. Difficult and intricate as the investigation may seem when extended to all the cases of vital phenomena, they are not so in the grosser examples to be now adduced; and if it should be found that many substances distinctly continuous with vital organic bodies are wholly subjected to physical dominion, and that several other substances are in part influenced by the one cause and by the other, it may perhaps open new and more precise views in the medical art. Those parts of living organic bodies which have no power of self repair, which hold no continuity with the fluid circulating material destined to replenish the waste, to augment the bulk, or repair the accidents of the living fabric, may be justly deemed extra vital. The exuvial coverings and defences of animals are of this kind, viz. hairs, nails, feathers, and all other cuticular structures, as well as the epidermoid coverings or husks of the vegetable kingdom. Some of those substances which are destined

to be worn away retain a partial continuity with the organic system of circulating fluids, as the organic bulbs of hair, the roots and lamellæ of nails and hoofs; whilst the other parts, which are destined to be shed, as feathers and cuticular scales, are wholly detached from the vascular communion after their complete formation, and only adhere mechanically to the living parts for a time.

The most apposite illustrations, and the most positive instances, of union between vital and extra vital parts are to be found in the testaceous tribe of animals. After a long continued and careful investigation, I am fully convinced that the shells of all the vermes of Linnæus are extra vascular from their commencement, and remain so during their whole connexion with the living creature. The first production and the growth of those shells always depends upon a deposit of the material thrown out from the surface of the body of the living animal. The figure and colours of the several parts of those shells in every species depend upon the shape and the colouring glands of the modelling organs: fractures are repaired by spreading a cretaceous fluid over the inner edges, and never by any exudation from the fractured parts, since they always retain the angular broken surfaces after such repairs. Extraneous bodies are equally coated with shell, whether they are in contact with the parent shell or not. The first may be seen in the frequent envelopement of Neides in the common oyster; and the latter has been often ascertained by experiments made for the purpose of creating artificial pearls, and which might, if skilfully practised, yet prove very successful. The borings of parasitical vermes into shells are never filled up, or the bored surfaces altered, unless such borings penetrate into the cavity where the living animal dwells, and then the apertures are invariably plugged up, or smeared over with pearly matter. The water-worn outer surfaces of old shells, and other external abrasions, are never repaired, which is to be seen in old living oysters exposed to the moving friction of currents or strong tides; in the worn-off spines of the pholas dactylis; and in the convex points of the two valves of old mytili, especially the mytilis anatinus. I have sought in the most extensive collections of the metropolis for examples of fractures, and other injuries, which have occurred to the shells of living vermes, and I have collected many remarkable specimens. They all demonstrate the same results, without any exception. I have made numerous experiments upon the garden snail (helix nemoralis), by fracturing and breaking away the shell in various parts; and have always found the repairs to be effected from within by first smearing over an epidermoid varnish, and then by plastering the inner surface of that film with successive calcareous laminæ. I have in vain attempted to inject the shells of recent vermes from the vascular parts of their bodies, and am fully -satisfied that none of their albuminous or gelatinous testaceous mem-branes were ever at any time permeable to vessels; indeed they do not possess any of the reticular texture or arborescent pores which are common to all vascular parts; but, microscopically examined,

they resemble the exuvial or epidermoid membranes. To these facts may be added the notorious circumstance of the unchangeableness of the outer surfaces of testaceous shells during their growth, and the continual renewal of their other surfaces, which admit of contact with the living inhabitant: next the stains and coloured transudations which they often derive from metallic salts and other colouring materials placed in their vicinity: and, lastly, that such occurrences do not affect the living animal. The mechanical connexion or contact that subsists between the living animals which occupy the testaceous shells, and their extraneous dwellings are in many instances very slender. The common oyster possesses its first pair of valves, consisting of single laminæ, before it quits the parental organs. A muscle passes between the centres of the cavity of each shell adhering to each, and it acts upon the valves nearly at right angles. The animal has no other continuity with the shells. At the hinge an elastic substance is wedged in, the spring of which is excited by compression, but it does not possess the property of extension beyond its passive state; when dried, this substance cracks into cubes. As the animal grows, it augments the margin of its shells, and thickens them by adding new laminæ on their insides. The muscular adhesion glides forward, still keeping to the centre of the valves. The elastic substance at the hinge is augmented along its inner surface only, and must have been always deposited during the expanded state of the valves, since the limit of its elastic condition is exactly adapted to that state. As the lamina of the shells increase, there is a gap at the outside of the hinge filled with soft, crumbling, and decomposing worn-out elastic ligament. This gap presents two inclined planes which meet in an acute angle, and that space is kept free from pebbles and hard extraneous bodies by the presence of the decomposing ligament, as such an accident would prove fatal by preventing the opening of the valves. The growth of all the testaceous shells affords remarkable proofs of their extra vascular formation. The muscular adhesions are generally the only parts of continuity between the animal and its shells, and these are constantly changing with the augmentations of bulk. In all the conoid univalves which revolve upon spiral axes the successive parts of the shell are merely spread upon the older parts without any intermixture of their substances, and epidermis or extraneous bodies are alike involved in the successive folds. In other classes of animals similar phenomena occur. The calcareous shells of birds' eggs are merely deposited upon the membrana putaminis, and the inner portions are regular crystallized prisms, the long diameters of which point to the centre of the egg. These shells are wholly extra vascular, and their albuminous membranes are alike cuticular, whilst the inner true membrana putaminis is made reticular, and capable of vascular organization. The order of deposit in these examples is like that of enamel in teeth, which appears to be precipitated the bone of the teeth under the guidance of a membranous case or mould. From a disordered fowl I have seen eggs produced, VOL. VI. N° III.

upon

M