7. I have already spoken of the action of oxide of silver on oxygenized muriatic acid, and I stated that these bodies by their mutual action produced water, the disengagement of oxygen gas, and the chloride of silver. But this chloride is violet. Now violet chloride, in what manner soever it is produced, leaves always a metallic residue when treated with ammonia—a phenomenon, which Gay-Lussac observed respecting the white cloride rendered violet by the action of light. It follows from this, that when oxygenized muriatic acid is treated with oxide of silver, a small part of the oxygen disengaged comes from the oxide itself. Consequently to determine, by the process, which I pointed out in the last paper, the quantity of oxygen in oxygenized muriatic acid by means of oxide of silver, we must take an account of the oxygen proceeding from that portion of oxide. To do this we must make a second experiment, in which we collect the chloride of silver, produced and mixed with oxide of silver. This mixture is treated with ammonia, and we obtain as a residue the portion of the metal that had been reduced. The quantity of this residue makes us immediately acquainted with the quantity of oxygen wanted.

I shall remark, with respect to the violet chloride of silver, that it probably corresponds with the protoxide of silver.

8. As soon as we plunge a tube containing oxide of silver into a solution of oxygenized nitrate of potash, a violent effervescence takes place, the oxide is reduced, the silver precipitates, the whole oxygen of the oxygenized nitrate is disengaged at the same time with that of the oxide; and the solution, which contains merely common nitrate of potash, remains neutral, if it was so at first.

9. Oxide of silver produces the same effects upon oxygenized muriate of potash as upon the oxygenized nitrate.

10. If silver in a state of extreme division be put into the oxygenized nitrate, or muriate of potash, the whole oxygen of the salt is immediately disengaged. The silver is not attacked, and the salt remains neutral as before. The action is less lively (indeed much less lively) if the metal be in a less divided state. In all cases the action is less violent in the muriate than the nitrate.

11. Silver is not the only metal capable of separating the oxygen of the oxygenized nitrate and muriate of potash. Iron, zinc, copper, bismuth, lead, platinum, possess likewise this property. Tron and zinc are oxydized, and, at the same time, occasion the evolution of oxygen. The others are not sensibly oxydized. They were all employed in the state of filings.

I tried likewise the action of gold and of tin. These metals do not act sensibly on the neutral solutions, or, at most, only a few bubbles are disengaged at intervals.

12. Several oxides, besides those of silver and mercury, are capable of decomposing the oxygenized nitrate and muriate of

potash. I shall mention in particular the peroxide of manganese and that of lead. Only a small quantity of these oxides.in powder is necessary to drive the whole of the oxygen from the saline solution. The effervescence is lively. I believe that the peroxide of manganese does not undergo any alteration. It is possible that the peroxide of lead may be reduced to a less degree of oxidation.

13. It is known that nitric acid has no action on the peroxide or manganese and of lead; but this is not the case with oxyge nized nitric acid. It dissolves both of them with the greatest facility. The solution is accompanied by a great disengagement of oxygen gas. Potash produces in the manganese solution a black, flocky precipitate; and in that of lead, a brick coloured precipitate. This last is less oxydized than peroxide of lead; for when treated with nitric acid, we obtain nitrate of lead and a flea coloured residuum. At the instant of the addition of the potash there is a strong effervescence.

14. The oxygenized sulphates, phosphates, and fluates, exhibit the same phenomena with the oxide of silver, with silver, and probably with other bodies, as the oxygenized nitrate and muriate of potash. The greater number of the oxygenized alkaline salts possess the same properties as the oxygenized salts of potash.

What is the cause of the phenomena which we have just stated? This is a question which we must endeavour hereafter to resolve.

For this purpose, let us recall the phenomena which oxide of silver and silver exhibit with the neutral oxygenized nitrate of potash. Silver in a fine powder rapidly disengages the oxygen of this salt. It undergoes no alteration, and the oxygenized nitrate is reduced to the state of simple nitrate.

The oxide of silver disengages still more rapidly than silver the oxygen of the oxygenized nitrate. It is itself decomposed; it is reduced; the silver is totally precipitated; and we find in the liquid only common neutral nitrate of potash. Now in these decompositions the chemical action is evidently null. We must, therefore, ascribe them to a physical cause; but they depend neither upon heat nor upon light. Hence it follows, that they are probably owing to electricity. I shall endeavour to ascertain this point in a positive manner. I shall endeavour to ascertain likewise whether the cause, be it what it may, cannot be produced by the contact of two liquids and even of two gases. From this, perhaps, will be derived the explanation of a great variety of phenomena.

ARTICLE IV.

On the Phenomena of Sanguification, and on the Blood in general. By W. Prout, M.D.

[PART of the following paper has already been laid before the public, under the title of an "Inquiry into the Origin and Properties of the Blood: " as, however, it was never completed, and as the work in which it appeared had a very limited circulation, the author has been induced to correct and republish the whole in a condensed and somewhat different form.]

The object of the present essay is to give a summary and connected view of what is known respecting the phenomena and intimate nature of sanguification. For a considerable proportion of the facts, I am, of course, indebted to others; but I flatter myself that my readers will readily excuse the introduction of these, on reflecting that the assistance of what is known is necessary to the further extension of knowledge, and to enable us to arrive at the unknown.

Perhaps, it may facilitate the perusal of these pages to premise, in general terms, the opinion which my observations have led me to form respecting the development and nature of the blood. the arrangement of the subject being chiefly founded upon that opinion. My notion is then that the blood begins to be formed, or developed from the food, in all its parts from the first moment of its entrance into the duodenum, or even, perhaps, from the first moment of digestion, and that it gradually becomes more and more perfect as it passes through the different stages to which it is subjected, till its formation be completed in the san guiferous tubes, when it represents an aqueous solution of the principal textures and other parts of the animal body to which it belongs.

The chief ingredients in the blood are albumen, fibrin, and the colouring principle, which may be supposed to represent the common cellular texture, the muscular texture, and the nervous texture,* respectively. These different principles are so nearly allied to one another in their chemical properties, that Berzelius has given them the general name of albuminous contents of the blood-a term which, for the sake of convenience, we shall adopt in the following inquiry.

The principal distinct stages in the formation of blood in all the more perfect animals are digestion, chymification, chylification, and sanguification, usually so called; the first process being

* I by no means wish to be understood to assert that the red particles of the blood are destined to form the cerebral and nervous substances of animal bodies. I believe, however, that they are more intimately connected with the nervous func tion than any other ingredient of the blood, as I shall attempt to show hereafter.

confined to the stomach, the second to the duodenum, the third to the lacteals, and the fourth to the blood vessels.

The properties of chyme,* chyle, and blood, the results of these processes, appear to run gradually and imperceptibly into one another, and hence, perhaps, they can hardly be considered as distinct and well defined steps in the general process of sanguification. As, however, the vessels, or organs, in which they take place are perfectly distinct, it becomes a matter of convenience to consider the processes themselves as distinct also. I shall, therefore, first consider the important function of digestion.

Phenomena, &c. of Digestion in a Rabbit.-A rabbit which had been kept without food for 12 hours was fed upon a mixture of bran and oats. About two hours afterwards, it was killed, and examined immediately while still warm; when the following circumstances were noticed:-The stomach was moderately distended, with a pulpy mass, which consisted of the food in a minute state of division, and so intimately mixed, that the different articles of which it was composed could be barely recognized. The digestive process, however, did not appear to have taken place equally throughout the mass, but seemed to be confined principally to the superficies, or where it was in contact with the stomach. The smell of this mass was peculiar, and difficult to be described. It might be denominated fatuous and disagreeable. On being wrapped up in a piece of linen and subjected to moderate pressure, it yielded upwards of half a fluid ounce of an opaque, reddish-brown fluid, which instantly reddened litmus paper very strongly, though not permanently, as upon being dried, or even exposed to the air for a short time, the blue colour was restored. It instantly coagulated milk, and, moreover, seemed to possess the property of redissolving the curd, and converting it into a fluid, very similar to itself in appearance. 'It was not coagulated by heat, or acids; and, in short, did not exhibit any evidence of an albuminous principle. On being evaporated to dryness, and burned, it yielded very copious traces of an alkaline muriate, with slight traces of an alkaline phosphate and sulphate; also of various earthy salts, as the sulphate, phosphate, and carbonate of lime.

Very similar phenomena were observed in other instances. The contents of the stomach uniformly reddened litmus paper, and, in general, coagulated milk (except in one instance, in which the animal had lately died, apparently from some injury of the stomach, which was quite crammed with food), when the property of acting upon milk was very weak, and appeared to be

* I use the term chyme in a sense somewhat different from that commonly employed, by limiting it to that portion of the alimentary matter found in the duodenum, which has already, or is about to become albumen, and thus to constitute a part of the future blood.

+ On looking at the litmus paper the next day, I observed it had again assumed a deep red colour, which was permanent. This curious fact will be noticed hereafter.

either neutralized or destroyed. In this instance also, the inner coat of the stomach, especially in the neighbourhood of the pylorus, was dissolved.*

Phenomena of Digestion in a Pigeon.-The animal, which was the subject of the present examination, was young, but fully fledged, and had been fed about two hours before it was killed upon a mixture of barley and peas. It was opened and examined immediately after death. In the crop was a portion of the food, which was swollen and soft, but appeared to have undergone no further sensible change than what might have been expected from mere heat and moisture. This organ did not exhibit any indications of the presence of an acid. The gizzard, or stomach, contained corn in various states of decomposition, the internal parts of some of the seeds being reduced to a milky pulp, which flowed out on their being subjected to pressure;

Since the above observations were published, Dr. Wilson Philip has given a more extended account of the phenomena of the digestive process in this animal; an abstract of which I shall lay before my readers.

"The first thing" says Dr. P. "which strikes the eye on inspecting the stomachs of rabbits which have lately eaten is, that the new is never mixed with the old food. The former is always found in the centre surrounded on all sides by the old food, except that on the upper part between the new food and the smaller curyature of the stomach, there is sometimes little or no old food. If the old and the new food are of different kinds, and the animal be killed after taking the latter, unless a great length of time has elapsed after taking it, the line of separation is perfectly evident, so that the old may be removed without disturbing the new food. "If the old and the new food be of the same kind, and the animal is allowed to live for a considerable time after taking the latter, the gastric juice passing from the old to the new food, and changing as it pervades it, renders the line of separation indistinct; but towards the small curvature of the stomach, and still more towards the centre of the new food, we find it, unless it has been very long in the stomach, comparatively fresh and undisturbed. All around, the nearer the food lies to the surface of the stomach the more it is digested. This is true even with regard to the small curvature compared with the food near the centre, and the food which touches the surface of the stomach is always more digested than any other found in the same part of the stomach. But unless the animal has not eaten for a great length of time, it is in very different stages in different parts of the stomach. It is least digested in the small curvature, more in the large one, and still more in the middle of the great curvature.

"These observations apply to the cardiac portion of the stomach." "The food in the pyloric portion of the stomach of the rabbit is always found in a state very different from that just described. It is more equally digested, the central parts differing less in this respect from those which lie next the surface of the stomach." "One of the most remarkable differences between the state of the food in the cardiac and pyloric portions of the stomach is, that in the latter it is comparatively dry; in the former, mixed with a large proportion of fluid, particularly when digestion is pretty far advanced, and time consequently has been given for a considerable secretion from the stomach."

Thus continues Dr. Philip: "It appears that in proportion as the food is digested, it is moved along the great curvature, when the change in it is rendered more perfect to the pyloric portion. The layer of food lying next the surface of the stomach is first digested. In proportion as this undergoes the proper change, it is moved on by the muscular action of the stomach, and that next in turn succeeds to undergo the same change. Thus a continual motion is going on; that part of the food which lies next the surface of the surface passing towards the pylorus, and the more central parts approaching the surface."

Dr. Philip has remarked, that the great end of the stomach is the part most usually found acted upon by the digestive fluids after death.