prompting them to a repair of whatever evils they may encounter, by the most skilful and definite methods.

In order to comply with this double demand of carrying off the dead matter, and of providing a substitute of new, each of the systems before us commences, in the living substance that immediately surrounds that which requires removal, a new mode and a new degree of action.

A boundary line is first instinctively drawn between the dead and useless, and the living and active parts; and the latter retract and separate themselves from the former, as though the two had been skilfully divided by a knife. This process being completed, the mouths of the surrounding absorbent vessels set to work with new and increased power, and drink up and carry off whatever the material may be of which the dead part consists, whether fat, muscle, ligament, cartilage, or bone; the whole is equally imbibed and taken away, and a hollow is produced, where the dead part existed. At the same time the mouths of the correspondent secernent vessels commence a similar increase and newness of action, and, instead of the usual lymph, pour forth into the hollow a soft, bland, creamy, and inodorous fluid, which is denominated pus; that progressively fills up the cavity, presses gradually against the superincumbent skin, in the gentlest manner possible distends and attenuates it, and at length bursts it open, and exposes the whole of the interior to the action of the gases of the atmosphere.

It was at one time conceived, and by writers of considerable eminence and judgment, and of as late

a date as the time of Mr. Hewson, that the injured and dead parts were themselves dissolved and converted into pus; but this opinion has been disproved in the most satisfactory manner by the minute and accurate experiments of Mr. John Hunter, Sir Everard Home, and Mr. Cruickshank; and the process has been completely established as I have now related it.

In what immediate way the gases of the atmosphere operate so as to assist the secernent mouths of what is now the clean and exposed surface of a wound, in producing incarnation, or the formation of new matter of the very same kind and power as that which has been carried off, and enable them to fill up the cavity with such new matter, and perfect the cure, we do not exactly know. Various theories have been offered upon this very curious subject; but at present they are theories, and nothing more; and I shall not, therefore, detain you with a relation of them. Thus much, however, we do know, that the co-operation of the atmosphere with the action of the mouths of the secernent system engaged in the work of restoration is, in some way or other, peculiarly beneficial; and that, generally speaking, the wider the opening, and the freer the access of atmospheric air of a due temperature to the surface of the wound, or, which is the same thing, the freer it comes in contact with the mouths of the secernent vessels, the more rapidly and auspiciously the work of impletion and assimilation proceeds. Neither do we know, precisely, why pus, rather than any other kind of fluid, should in the first instance be poured forth, for the purpose of filling up the hollow, and producing a rupture of

the skin; but we know to a certainty that some such general process is in most cases absolutely necessary; we know that such a rupture must take place in the natural mode of cure; that the atmosphere must come into close contact with the mouths of the restorative secernents; that a milder or softer fluid could not possibly be secreted for such a purpose; and that the entire process exhibits proofs of most admirable skill and sagacity. It is at times possible for us to assist the process by the lancet, which accelerates the opening. Yet, even in this case, we do no more than assist it, and are only, as we ought ever to be in all similar cases, humble coadjutors and imitators of nature, and admirers of that all-perfect and ever-present wisdom which we are so often called upon to witness, but are never capable of rivalling.

A process closely similar to this is perpetually unfolding in vegetable life. And it was merely by taking advantage of this process that Mr. Forsyth was able to make old, but well-rooted, stumps of fruit-trees throw forth, far more rapidly than he could saplings, a thrifty family of vigorous and well-bearing shoots: for the compost for which he was so celebrated does nothing more than merely increase the secernent and absorbent action of the vegetable frame by its stimulating property, and defend the wounded part to which it is applied from being injured by the inclemency of the weather.

From what has thus far been observed, it appears obvious that all the different parts of the living body are assimilating organs, or, in other words, are capable of converting the common nutriment of

the blood into their own respective natures, and for their own respective uses. And it has also appeared, that under particular circumstances every part is capable, moreover, of secreting a material different from that of its own nature; as, for example, the material of pus, whenever such a substance is necessary.

This view of the subject will lead us to understand with facility how it is possible for various organs of the system to maintain two distinct secretions at the same time: one of a matter similar to its own substance, and exclusively for its own use; and another of a matter distinct from its own substance, and in many instances subservient to the system in general.

Of this last kind are the stomach, the liver, the respiratory organ, and the brain; each of which secretes, independently of the matter for its own nourishment, a matter absolutely necessary to the health and perfection of the general machine; as the gastric juice, the curious and wonderful properties of which I described on a former occasion; the oxygenous principle of the inspired air, and, as some suppose, those of light or caloric; the bile; and the nervous fluid, or material of sensation.

There are various other organs, of a smaller kind and simpler texture, which also perform the same double office, and secrete materials of a much more local use, or which are intended to be altogether thrown away from the system, as waste or noxious bodies. And to the one or the other of these classes belong the kidneys, the intestinal tube, the minute and very simple perspiratory follicles of the skin, the delicate organs that separate the saliva and mucus that serve to lubricate the mouth and

nostrils, and those that elaborate the tears, the wax of the inner ear, and the fat.

The organs, of whatever size or texture, that perform this double function, are called secretory glands; and they are distinguished into different sets, either from their peculiar office or peculiar structure as salivary, lachrymal, mucous, which are denominated from the former character, and apply to the smallest and simplest of them; conglobate, which are of a larger form, and of an intricate convolution, and belong exclusively to the absorbent system, as the mesenteric and lumbar and glomerate and conglomerate, which are composed of a congeries of sanguineous vessels, without any cavity, but with one or more mouths, or excretory ducts as they are called, which, in the latter, open into one common trunk,- as the mammary and pancreatic; both which kinds are denominated from the character of their structure.

It is by this peculiar organization in animals and plants that all those nice and infinitely varying exhalations or other fluids are thrown forth from different parts of them, by which such parts, or the whole individual, or the entire species of individuals, are respectively characterised. Our own senses are too dull to trace a discharge of any kind of essence or vapour from the surface of the human skin in its ordinary action; but the discoloration which soon takes place upon the purest linen, when worn in the purest atmosphere, sufficiently proves the existence of such an efflux; and there are various animals whose olfactory organs are much acuter than our own, as our domestic dogs, for example, that are able to discern a difference in the odour of the

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