place under certain circumstances. If you place an animal membrane in contact with water, it soon becomes saturated or filled with that fluid. If you place that membrane in contact with a compound fluid, say, spirit or water having colouring matter in solution, the membrane will positively decompose that compound, and reduce it to its component parts.

If you place one extremity of a piece of membrane in a vessel containing a coloured tincture, that is, a spirituous solution, say, of iodine, whilst the other extremity be kept out of it, that part of the membrane which has contact with the tincture will immediately assume its colour; because the iodine passes perfectly through the membrane; and, mark you, this dark coloured part of it is bounded by a fixed line, and just above this you will find that the membrane is penetrated by another and different part of the tincture; this is the colourless alcohol in which the iodine was dissolved; above this you will discern evident traces of another and lighter-coloured fluid, which is the small portion of water necessarily present in alcohol.

Likewise, if you place a piece of animal membrane in a glass of port wine, you will soon notice the same kind of decomposition. On the lower part of the membrane you will have the colouring matter of the wine; above this will be the spirit or alcohol; and above this you will have the water.

This most interesting subject of membranous absorption has been minutely investigated and ably explained by Liebig; and by many and various experiments he has proved the fact of decomposition of compound fluids by membranes. That whilst a membrane is imbibing compound substances in fluids, it also reduces them into their component elements.

Further, Liebig has found by experiments that the membranous absorption and decomposition of compound fluids take place in different degrees of facility, according to the nature of the compounds absorbed and decomposed. You will do wisely in recollecting these particulars; and that similar properties belong to living membranes. For instance, that the mucous membrane lining the stomach absorbs and. also decomposes

different matters contained in its fluid contents: and that, consequently, living membranes in all animals perform important functions.

I have next to instruct you respecting a remarkable property of membrane, which is now frequently referred to by intelligent physiologists, and which you must understand, in order to properly comprehend the principal subjects of these letters. I believe that it was first noticed by M. Dutrochet; and afterwards investigated more fully by Brucke; and ultimately established by Liebig. I allude to the membranous process termed, in technical language, endosmose and exosmose. It is that process by which fluids in contact with both surfaces of a membrane pass through it in currents which proceed in opposite directions. This takes place according to the different qualities of the fluids, and especially in relation to their density or consistence.

M. Dutrochet took certain membranous bags, which form a part of the intestines of fowls, and filled them with fluids of different density: one he filled with milk, another with syrup, another with mucilage of gum arabic. He then tied those bags securely, and placed them in a large basin of water. He soon found that an interchange of the fluid within and without the bags began to take place by currents through the membrane of which they consisted; and that these currents flowed in an opposite direction to each other. The current from without inwards was formed by the flow of the external water towards the denser fluid contained in the bags. The other and weaker current was from within outwards, and it was the flow of the denser fluid within the bags to the external water. The first mentioned, or in-going current, is called endosmose, from the Greek word endon, within, and osmos, impulse. The other, or out-going current, is called exosmose, from ex, out, or outwards, and osmos.

Liebig and others have investigated this process of endosmose and exosmose, especially in connection with vegetable membranes. It is, indeed, of extensive application to the physiology of plants. But it becomes of much more weighty concern in its

application to human physiology. I shall not undertake, in my limited space, to instruct you very minutely on the many interesting particulars of its application. You can readily suppose that it has greatly to do with the vital processes of the human body, which are performed in its various cells, cavities, and myriads of capillary vessels.

You must consider it as an established fact, that all the animal tissues have a powerful and innate property which enables them to transmit fluids, and also solids which are of a soluble kind, through their substance. Remember that membranous tissue becomes the agent by which this is effected, whether it be proper membrane, or in the form of the coats of blood-vessels; that by means of this property both fluids and solids are absorbed by the human body, with whatever surface or whatever organ of it they may be in contact. It will matter not whether that contact be with an internal or an external surface, or whether with the stomach, or the lungs, the liver, or the heart; whether it be with the mouth, or the eye, the nose, or the ear.

You can well suppose that this important property of membranes must have a weighty bearing on the concerns of health and disease; also that it must possess great influence in connection with the functions of the three great absorbing surfaces of the human body; namely, that of the lungs, the stomach, and the skin,

There can be no reasonable doubt but that this action of the membranes, in the transition of matters through their substance, affords the most satisfactory explanation of the extraordinary efficacy of certain processes of the water cure. It must at once strike your mind, that especially in the water compresses both local and general, and above all, in the wet-sheet packing, the whole arrangement becomes highly favourable for the effective agency of endosmose and exosmose. This I regard as an established fact; and in it you will perceive that there is the most rational cause for the highly curative power of these water processes. It most satisfactorily explains to us how it is that so much and such various kinds of noxious matters are

drawn out of the body, through the skin, by such means. No doubt there is constantly the operation of endosmose and exosmose whenever the compresses and wet-sheet packing are applied, although the extracted matter may not be visible to

the eye.

Frequently, however, the fact of the extraction of noxious matter from the body by compresses and the wet sheet is known by its actual appearance in large quantity, and of a very offensive odour. I have witnessed it very often. I have seen the whole wet sheet of quite a yellow colour with the bile it had extracted from the human body, which was being poisoned by its presence throughout its textures. The wet packingsheet is frequently so saturated with the offensive matter it has extracted, that it has to be removed from the room as soon aș it has been taken from the patient.

During my three years' stay at Malvern, in the large and excellent hydropathic establishment of Dr Wilson, these things were of common occurrence, and came under my own observation in the many patients under my care in colleague with that shrewd and experienced practitioner of the water cure. Whenever I applied the compresses or the wet-sheet packing in cases of chronic diseases, especially of the liver, and in which much drug treatment had been previously undergone, I always calculated on seeing the extraction of these noxious matters.

I am glad to know that you have been instructed on the effective and scientific agency of the water processes, and that you also know of the extraordinary cures which have been accomplished by water treatment. You now can see the absurdity of those professional opponents who affect to sneer at the water cure. This kind of absurdity is a common thing with mankind, in opposing and vilifying that which they do not understand, and even have not seen. It just occurs to me here that the excellent physiologist of our day, Dr Carpenter, writes a paragraph in his work on human physiology, which is not very far off this kind of absurdity. He certainly displays his ignorance of the water cure when alluding to the wet-packing sheet. He writes of it-" The hot-air bath, in some cases, and the wet

sheet (which, as used by the hydropathists, is one of the most powerful of all diaphoretics)." It is not a diaphoretic at all, as the word is understood amongst medical men. He couples this wet sheet with the lamp-bath, and yet no two processes can be more different from each other in every respect. He writes further: "The absurdity of hydropathic treatment consists in its indiscriminate application to a great variety of diseases: no person who has watched its operation can deny that it is a remedy of a most powerful kind; and if its agency be fairly tested, there is strong reason to believe that it will be found to be the most valuable curative means we possess for various specific diseases, which depend upon the presence of a definite ' materies morbi' in the blood, especially gout and rheumatism; as well as for that depressed state of the general system which results from the 'wear and tear' of the bodily and mental powers." Dr Carpenter here takes a very limited view of the true nature of the water cure. Safely can I aver that no system of treatment ever yet propounded to mankind is so well adapted for the cure of all really curable diseases, and for alleviation of those which are incurable, as is the great water cure.

To return to membranous absorption. There is so much to instruct and interest you in direct connection with the absorbent function of the three great organs already stated, namely, the lungs, the stomach, and the skin, that I must inform you respecting them. Their internal surfaces possess great power of absorption, although in very different degrees. That of the lungs is, indeed, much the most powerfully absorbing surface of the human body. This is established on different grounds. Firstly, on the ground of the very great extent of membranous surface which is formed by the air cells; and, at the same time, that the membrane itself which composes them is so delicate and so fine in texture. Again, a free communication exists between the branches of the blood-vessels of the lungs, both veins and arteries. Again, the lungs themselves are adjoining, or rather, in actual contact with the heart, so that the course of the blood from the minute vessels of the lungs becomes short