red colouring matter, one would think he was looking at true blood.— In fact, let a certain quantity of white of egg be dropt into an excess of concentrated hydrochloric acid; the albumen, at first coagulated white, will very soon dissolve in the acid, taking on a violet colour which will afterwards pass into a blue. If the hydrochloric acid be now decanted and left to spontaneous evaporation, a white powder will be precipitated, which under the microscope will be seen to consist of very small, sphe rical globules, equal in size, and which the most practised eye might easily mistake for the globules of the blood.

"Now it will be easily granted that the quantity of these globules will vary according to the quantity of the menstruum which will evaporate in a given time, and according to many other accessory circumstances; so that these globules might present themselves in different forms and magnitudes, according to the age, habits, species and sex of the animals submitted to observation.

"Besides these albuminous globules, the blood still contains a large quantity of liquid albumen; a fact of which the microscope may assure us, either by our letting blood, diluted with water, dry spontaneously, (we then see, in fact, a layer of albumen which cannot be produced by a junction end to end of the globules,) or by coagulating it with alcohol. Keeping the eye at the microscope, globules are seen enveloped by a membranous coagulum which is unexpectedly formed at the expense of the liquid portion.

"Let us now endeavour to discover the nature of the menstruum which renders this albumen soluble, and which, by being neutralized or by its evaporation deposits the globules which swim in the serum, or are carried along the vessels without uniting with each other. The analogy of chemical composition and of circulation between the liquid of the chara and the blood, induced me at first to think that the menstruum of the albumen was, in both, acetic acid. Macquer and Homberg had already discovered an acid in blood; 'Prévost had found acetic acid in it; Berzelius had shown the presence of lactate of soda and potash not only in the blood, but in all the tissues. This lactate we have demonstrated to be but an albuminous acetate of soda and potash. This hypothesis was, it is true, in opposition to the evident alkaline nature of the blood at the moment it leaves the vessels, but this alkaline condition might be consecutive to an acid state, and that might occur which we have already had occasion to verify, with regard to an acid ammoniacal salt becoming blue by contact of the atmosphere. But the constant alkaline nature of the most recently drawn blood, and the coagu. lation produced by diluted acids, gave no room to doubt but that the menstruum of the albumen was an alkali. This alkali is soda, and above all, ammonia, of which authors take no account, and whose various salts are recognized under the microscope.

"This principle once admitted, the spontaneous coagulation of the blood no longer offers any inexplicable difficulty. For the carbonic acid of the atmosphere, that which is formed in the blood by its avidity for oxygen, or that formed in consequence of the spontaneous fermentation of the elements of the blood itself, saturates the menstruum of the albu men, which is precipitated in the form of clot. The ammonia and water

of the blood which springs smoking from the vein, by being evaporated, abandon in time a proportional quantity of dissolved albumen, and the mass coagulated so much the sooner, the less the blood contains of water. I might add that an acid fermentation is susceptible of being manifested in a liquid raised to the temperature of 98° Fahr., and containing at the same time insoluble albumen and sugar, immediately on its exit from the vessels. This acid will render the saturation of the

menstruum still more rapid."

This theory of Raspail is certainly a very ingenious one, but it is as untenable as it is ingenious. In the first place, it is opposed to the facts developed by the experiments of Sir C. Scudamore. It will be remembered that in those experiments coagulation was hastened by the evolution of carbonic acid gas under the receiver of the air pump, and that too, though the temperature was lowered. It is opposed, too, to the fact that arterial, coagulates more rapidly than venous blood. Admitting that there is an increase of fibrin in arterial blood and a less quantity of water, still there is certainly a much fess quantity of carbonic acid, for this last has been evolved from the venous blood in the respiratory process. Moreover, Sir H. Davy could distinguish no difference in the time required for coagulation when the blood was subjected to the influence of carbonic acid gas.

Nervous Theory.—Mr. Thachrah in his "Inquiry into the nature and properties of the blood," comes to the conclusion that "the vital or nervous influence is the source of the blood's fluidity, and its loss the cause of coagulation."

Mayer of Bonn, came to a like conclusion from some experiments upon the nervus vagus. Dividing those nerves, he found the blood coagulated in the arteries and veins of the lungs, and also in the heart. "But," says Müller, "I have repeated the experiments without obtaining the same result."+

But be the fact so or not, it is impossible to refer the coagulation of blood to the want of nervous influence. The nerves cannot possibly act upon the mass of the blood contained in the larger vessels. They may, to be sure, exert an indirect action upon this fluid in the nutritive process-when molecules of blood come in contact with molecules of the solids-but they exert this influence indirectly, and by means of primary changes induced in the solids. A sufficient answer, however, to any such theory, is found in the fact that blood effused into the tissues from contusions, that contained in the extremities of arteries that have been tied, as in amputations, &c., coagulates, becomes organized and a part of the living tissues. Moreover, in certain diseases, such as Asiatic cholera, the blood is found fluid after death, and uncoagulable. It is hardly worth while to mention that in such a disease the influence of the nervous system must be nearly annihilated.

Vital Theory.-This theory bears two phases;-one attributes coagulation to some unknown mode of action of the vital principle; the other to the loss of the vital principle, in other words, to the death of the blood. The celebrated John Hunter is the coryphoeus of the first. As, from many experiments, he knew it to be true that this remarkable change Elements of Physiology, p. 358.

* Chimie organique, tom. iii.

depended neither upon rest, nor upon the lowering of the normal temperature, nor upon the presence and contact of the atmosphere, nor upon a difference in the nature of the substances in contact with the blood; and as he supposed that he had considered all the circumstances of the case, he naturally inferred that the phenomenon was not due to any of these circumstances, nor to any combination of them, but to something in the blood itself-and this was the vital principle. He uses the fol lowing language with regard to this subject. "Coagulation, I conceive to be an operation of life; and I imagine it to proceed exactly upon the same principle as the union by the first intention; it is particle uniting with particle, by the attraction of cohesion, which in the blood forms a solid."

One would suppose, à priori, that as the blood is taken in a fluid state from the living body and then changes its form, that the cause of the change was a loss of the vital principle; provided the existence of such a principle be admitted. But as coagulation is an operation of life it was incumbent upon the theorist to tell us what was the cause of its fluidity in the vessels. It might be pertinently asked if the fluid blood in the living body was dead matter? Coagulation is an operation of life-now what is the cause of its being constantly found fluid in the vessels of a healthy man?

In reply, we have the following strange language. "While the blood is circulating, it is subject to certain laws, to which it is not subject when not circulating. It has the power of preserving its fluidity, or in other words, the living principle in the body has the power of preserving it in this state." Again, "If the blood had not the living principle, it would be, in respect of the body, as an extraneous substance. Blood is not only alive itself, but is the support of life in every other part of the body."

So, coagulation is caused by the living principle, and the very reverse condition (that of fluidity) is caused by the same agent. But it is evident, that until we are informed how this principle operates in the two cases, we are just as wise as we were before.

Puzzled in the extreme by the perplexities of this subject, Hunter, at last, as if in desperation, uses the following extraordinary language.The passage has been often quoted and needs no comment. "My opinion is, that the blood coagulates from an impression—that is, its fluidity under such circumstances being improper, or no longer necessary, it coagulates to answer now the necessary purpose of solidity. This power seems to be influenced, in a way in some degree similar to muscular action, though probably not entirely of that kind; for I have reason to believe that blood has the power of action within itself, according to the stimulus of necessity, which necessity arises out of its situation."

Let us now turn to the other phase of this theory-to the views of those who contend that fluidity is owing to the vital principle, and coagulation to the death of the blood. It is obvious that such a theory cannot account, for many familiar phenomena, indeed is opposed to them, and theory must always fall when arrayed in opposition to facts. We know that blood, extravasated into the tissues, will coagulate, become organized and part of the living system. It may be converted into various tissues, take on inflammatory action and the various phenomena of disease. The clot left in the extremities of divided vessels after being

tied, becomes organized and is not distinguishable from similar tissues. If the coagulation is caused by death of the blood, how can all this happen? Again, in certain kinds of death, as from lightning, malig nant diseases, collapse of cholera, etc., the blood remains fluid. Is its life the cause of its so remaining?

Dr. Carpenter in his work on Human Physiology, seems to be of the opinion of Hunter, or at least to have adopted a similar one. "That the coagulation of the fibrin is not," says he, "as some have supposed, a proof of the death of the blood, but is rather an act of vitality, appears evident from what has been already stated of the incipient organization which may be detected even in an ordinary clot; and still more from the fact that, if the effusion of fibrin takes place upon a living surface, its coagulation is the first act of its conversion into solid tissues posses. sing a high degree of vitality. It is absurd to suppose that the blood dies, in order to assume a higher form. When withdrawn from the body, however, the coagulation of the blood is the last act of its life; for, if not within the influence of a living surface, it soon passes into decomposition."

This is singular language from an author who has so ably contended that life is not something superadded to matter.

But what is the use of so many words to tell us two well known and familiar facts, namely, that fibrin will coagulate in the body and become organized; and, that it will coagulate out of the body and then in due course of time pass into decomposition; for, to so much, and so much only, the passage amounts. But in all, is there one single circum. stance mentioned which throws light upon the question, why the fibrin in either case passes from the fluid to the solid form?

That the fibrin will be organized in the one case, and pass into decomposition in the other, like all animal matter under similar circumstances, is perfectly plain when the different conditions under which they exist are considered.

*

*

We have seen all the foregoing theories insufficient to account for the transformation of fluid fibrin into the solid state. It is not my purpose to offer another view of this singular phenomenon, but to point out that there are similar phenomena among artificial compounds, and to show that an explanation of the change in the blood can only be hoped for from the progress of chemistry. To that science the problem properly belongs, and by it will doubtlessly some day be solved.

It is well known that fibrine and albumen are closely allied, if indeed as some suppose, they be not identical. The word fibrine may therefore, with propriety, be substituted for albumen in the following extract from Dr. Turner's chemistry. "Were I to hazard an opinion on this subject, it would be the following: that albumen combines directly with water at the moment of being secreted, at a time when its particles are in a state of minute division; but as its affinity for that liquid is very feeble, the compound is decomposed by slight causes, and the albumen thereby rendered quite insoluble. Silicic acid affords an instance of a similar phenomenon."

Of silicic acid, he says, "In its solid form silicic acid is quite insoluble in water; but Berzelius has shown that if presented to water while

in the nascent state, it is dissolved in large quantity. On evaporating the solution gently, a bulky gelatinous hydrate separates, which is partially decomposed by a very moderate temperature, but does not part with all its water except at a red heat."

This, to be sure, does not explain the coagulation of fibrine, since the slight causes spoken of are the very things which we are in quest of.— But Dr. Turner's remarks evidently point to the general manner in which the phenomena may occur, as well as to an analogous pheno

menon.

But we may point to several other phenomena still more closely resembling the coagulation of the blood, and it will be seen that they too are, in the present state of science, inexplicable. Chemists, when speaking of these phenomena, are forced to use metaphorical language, and therefore employ the expression that the change is spontaneous; which, in other words means that they are ignorant of the cause of the effect. It is surely not worth while to argue that there can be no spontaniety of action except in beings possessed of volition.

The first of the phenomena alluded to which we shall mention, is the singular change which takes place in cyanic acid from no known cause. Graham thus describes it: "It is a transparent, very volatile liquid of a pungent odour, highly corrosive, miscible with water. Soon after its preparation this liquid spontaneously undergoes a very extraordinary change it is converted with the evolution of heat into a white solid matter, cyamelide, having the same composition in 100 parts, but insoluble in water and dilute acids, dissolved by caustic alkali, with the formation of ammonia, a cyanate and cyanuret of the alkali."

The next substance which we shall mention, subject to spontaneous change is chloral-" chloral," says Professor Graham "is a pretty oleaginous liquid, colourless, greasy to the touch, having a penetrating, disagreeable odour which provokes tears; its taste is first oily and then caustic. Its density is 1.502 at 64.4° (18° Cent.) and it boils at 201.2° (94° Cent.) distilling without alteration," etc.

"Like aldehyde, pure chloral cannot be kept long without alteration. It gradually passes into a solid mass, resembling porcelain, without change of weight, and equally whether contained in vessels hermetically sealed or open. This mass is not dissolved by water," etc.

But a still stronger example of these spontaneous changes is to be found in the substance termed aldehyde. I shall quote from Liebig's Animal Chemistry. "Among those substances which contain no nitrogen, we have aldehyde-a combustible liquid miscible with water, which boils at the temperature of the hand, áttracts oxygen from the atmosphere with avidity, and is thereby changed into acetic acid. This compound cannot be preserved, even in close vessels; for after some hours or days, its consistence, its volatility and its power of absorbing oxygen, all are changed. It deposits long, hard, needle-shaped crystals which at 212o are not volatilized, and the supernatant liquid is no longer aldehyde. It now boils at 140°, cannot be mixed with water, and when cooled to a moderate degree, crystallizes in a form like ice; nevertheless, analysis has proved, that these three bodies, so different in their characters, are identical-in composition."