an albumino-fibrinous blastema, in which special corpuscles (the pus-cells) are formed; the other transudes, not only through the capillary walls, but through the basement-membrane of the mucous surface, with more or less of attached epithelium, and in so doing experiences a peculiar modification, which remains impressed upon it, while the corpuscles mingled with it are either the natural cell-growth of the surface, or such as form naturally in blastemata, that are destined to become effete. Mucus, it is evident, is effete, like pus. It is hardly possible that any part of it should be absorbed again. A constant flow of it becomes, therefore, a serious drain upon the system, entailing a loss of so much protein matter. The old question, as to the means of distinguishing between pus and mucus, is manifestly of little moment, and has, in general, no interest for the practical physician. It is sufficient to state that the liquor puris is albuminous, the liquor muci not so; that pus will mix with water, and mucus will not; that pus is dissolved, in some measure, by acetic acid, while mucus is coagulated; and that mucus generally contains traces of epithelium, while pus does not. It may, however, be observed, that if a fluid, secreted under inflammatory irritation, should lose the characteristic tenacity of the liquor muci, and come to contain albumen, there would be considerable reason to fear that the texture of the mucous membrane had become ulcerated, and that the albuminous exudation, no longer modified to mucus, was being poured out from exposed vessels. Any admixture of blood with the secretion would render this still more probable.

Having considered the effusions of inflammation, we come next to examine the various changes that may take place in a part inflamed. We enumerate these as: (1) Enlargement; (2) Atrophy; (3) Ulceration; (4) Gangrene. The term "enlargement" is preferable to that of "hypertrophy," which is sometimes employed, because it conveys no such erroneous idea as that the part is truly increased in size by addition of more of its own proper substance, an occurrence which most rarely, if ever, is the result of any form of inflammation. The enlargement depends entirely on the infiltration of the tissue with some form of exudation matter, which subsequently undergoes metamorphoses such as we have described, and is more or less completely absorbed. It often happens, however, that a part remains behind, and is converted into a low form of fibroid tissue, or a semi-solid blastema, imbedding multitudes of nuclear particles.. This constitutes induration-matter, which resembles very much that which forms cicatrices; like which, its tendency is to contract and shrink, thus compressing and obliterating the vessels of the part, and in this way, as well as by its pressure, inducing the atrophy of the tissues among which it is deposited. A good instance of primary enlargement and subsequent atrophy, resulting from inflammation, is afforded by some cases of cirrhosis of the liver. Rokitansky describes atrophy, the result of inflammation, as depending upon the mechanical injury done to the tissues, in the seat of inflammation, by the exudation, as well as upon their being deprived by it of their proper amount of nutrition. Being thus rendered unfit for the discharge of their function, they fall to pieces, and are absorbed, together with the exudation. This occurs with especial frequency in delicate, lacerable tissues, when

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large quantities of exudation have been effused, and such as are solid and capable only of slow reabsorption. Thus, in the inflammatory foci, the substance of the brain, of the muscles, of the kidneys, &c. becomes lost, while there remains in its place one or more gaps, limited by cicatrix-tissue, which, if such gaps are small and numerous, causes a spongy, rarefied condition of the tissue."

Ulceration implies that condition of a part in which more or less of its proper substance has become eroded, and has disappeared, in consequence of unhealthy action, so that a cavity remains. This condition does not most commonly exist alone, but together with a greater or less amount of exudative and organizing processes. These are so far from being essential to it, that they constitute, in fact, the means by which its ravages are repaired; the formation of granulations, and the effusions of pus, are the characters, not of an extending, but of a healing ulcer. Instances of pure and simple ulceration are to be seen in the cornea, and in some ulcers of the walls of the stomach; they penetrate the tissue more or less deeply, so as sometimes to perforate it, without any surrounding thickening from the deposition of lymph. When the erosion of the tissue goes on rapidly and extensively, forming a sore, with very irregular surfaces and margins, and presenting no trace of reparative action, the ulceration is said to be phagedenic. Many other varieties of ulcers are mentioned, but they all have reference to the amount and character of the exudative and reparative processes taking place; and though they afford excellent indications of the condition of the general system, which are well worth studying, they are not to be regarded as containing anything special in the nature of the ulceration itself. Rokitansky considers that the main circumstance determining ulceration, is the corrosive quality of the exudation, the ichor. We agree with Mr. Paget in doubting the correctness of this as a general statement; it is much more probable that, in consequence of altered and defective nutrition, the tissue gradually deliquesces (so to speak) into a fluid, returning thus, though spoiled and effete, to the form of the healthy blastema, from which it originated. It is matter of some dispute whether the tissue, as it decays and is destroyed, is removed by absorption, or is cast off from the broken surface. Mr. Paget inclines to the opinion that it is ejected, resting upon the analogy of excreting surfaces, on the discovery of fragments of bone and phosphate of lime in ulcers of osseous structures, and on direct observation of the commencement of ulcers. We are also inclined to think that the process of removal is rather by ejection than by absorption, especially in the case of open ulcers, yet so that some amount of absorption also takes place, varying in degree in different cases, and probably even predominating in those where there is no external outlet. The formation of ulcerations on the surface of the cervix uteri, has appeared to us to take place in the following way, much as it is described by Dr. Baly on the intestinal surface: As the first step, in the situation of a spot of hyperæmia, a minute vesicle is formed, the epithelial layer being lifted up by effused fluid, while the tissue beneath is softened, loosened up, and appears less dense than natural. Afterwards the covering of the vesicle is detached, the fluid escapes, and the tissue beneath appears still more lax and

spongy, and has evidently undergone loss of substance. The hyperæmia, persists. In this case, we feel little doubt that the deliquescing tissue is partly thrown off in the fluid which escapes from the vesicle, partly absorbed by the blood vessels.

It seems desirable to indicate the difference which exists between ulceration and absorption. In both, there may be considerable loss of substance at some one or more points of the part affected, but in ulceration there is always an unhealthy state of the nutrition of the tissue, there is disease of it; in absorption, this is not the case: the part may be diminished, but cannot be said to be diseased. Contrast a bone, carious and ulcerated from inflammation, with one which has undergone absorption, in consequence of the pressure of an aneurism.

The last result of inflammation which we have to mention is Gangrene, or Mortification. This, indeed, is not a very common termination, nor is it at all peculiar to the inflammatory process. It more really belongs to a deficient condition of vital power induced by various causes, which may of itself be the cause of the death of some part, or render it so feeble that it perishes under injurious influences which would otherwise have had no such effect. Gangrene may ensue from the following causes: (1) from an absolute and prolonged stagnation of the blood; (2) from a defective supply of blood; (3) from a general taint or unhealthy crasis of the mass of the blood; (4) from a local injury. The absolute stagnation of the blood in the first case may be the result of violent inflammation, especially of an asthenic kind, and occurring in debilitated systems and organs; or it may be brought about mechanically, as when a portion of intestine is strangulated. Rokitansky says, that in this case the blood stagnant in the vessels first undergoes gangrenous decomposition, and that, exuding through their walls in the state of gangrenous ichor, it sets up the same decomposing change in the surrounding tissues, which break up into a dark-colored pulp, of as little consistence as tinder; diffluent, and excessively stinking. In the second case, besides various kinds of obstruction of the arteries from external pressure, their channels may be blocked up by extensive fibrinous coagula, either forming spontaneously, or in consequence of disease of the coats of the vessels. Gangrene occurring in aged persons, without any apparent cause, that from the use of diseased grain, and hospital gangrene, are instances in which the morbid action is dependent on a general taint of the blood, or decay of the whole system. Mr. Simon suggests that the mode in which ergot of rye produces its fatal effect, may be by causing such contraction of the blood vessels as prevents the flow of blood into the more distant parts, which consequently fall into the condition of dry gangrene. Spontaneous gangrene in old persons, or others, in which after death no obstruction of the bloodvessels is found, can only depend on an actual and premature loss. of vitality in the part affected, the tissues of which are no longer able to carry on the actions of vital chemistry, and yield to those of inorganic, i. e. decompose, before the death of the system has actually occurred. In gangrene, from local violence, or from frost-bite, &c., the vitality of the tissues of the part is destroyed by the injury done to them. The general characteristic of gangrene in all these cases is the failure of

vital action; decay and death in the tissues, intense inflammation, absence of blood-supply, a poison circulating in its current, senile decrepitude, a fearful laceration, may all have the effect of dissolving the vital affinities which hold together the elements composing the complex substances of our organism, and allowing them to fall back, as they naturally do, into the simpler compounds of inorganic chemistry. The distinctions of dry and moist gangrene, of black and white, of inflammatory and cold, have reference very much to the state of the affected part, with regard to the supply of blood. If the gangrene have its origin in inflammation, there will be a considerable quantity of fluid ichor effused, and the color of the part will be of a deep red, or almost black. On the contrary, if the gangrene depend on deprivation of the supply of blood, the part will be more dry, and of a pale color. Sometimes, especially from the effect of ergot of rye, a limb dries and shrinks up, becomes mummified, as it is said, with little change in color. A black color is, however, often observed in parts affected by gangræna senilis; this, no doubt, depends on alteration of the blood in the vessels, though there is often no hyperæmia. Soft tissues are more liable to mortify than such as are of a firmer consistence; bones, elastic and fibrous tissues, resist longer than muscles and mucous membranes; the large vessels and nerves are sometimes seen completely exposed by the ravages of hospital gangrene, all the tissues being removed from around them.

The constitutional disturbance which often supervenes on gangrene is easily to be accounted for by the absorption of decomposing matters into the blood, which act as a virus upon it, and render it unfit to maintain healthy action.

PYEMIA.

Proceeding to consider various diseased states of the blood, we come next to one, in which a product of inflammation, viz: pus, is believed in some way to be mingled with the blood, and, by poisoning it, to produce both general fatal depression of the powers of life and local purulent accumulations, the so-called secondary depots, in various important organs. The phenomena observed in pyæmia are somewhat as follows: A man has received an injury, or undergone some surgical operation, it may be an amputation, or that for fistula in ano; for a time all proceeds well, but soon shiverings come on, with adynamic fever and oppression, he emaciates, pain or disorder shows itself in some internal viscus, and in a few days he dies in a state of stupor, or delirium. On opening the body, the blood is found less coagulated than is natural; there are abscesses more or less numerous commonly in the liver and lungs, and often in other parts; there is frequently purulent effusion in the cavities of the joints, and sanguineous or purulent effusion in the serous cavities also. The question to determine is, how these morbid changes are brought about. From the almost invariable occurrence of such phenomena in persons who were the subject of suppuration, or in whom it was reasonable to believe that pus might be formed in the seat of some

injury, it was natural to conclude that the pus, making its way into the blood, was the cause of the mischief. This was confirmed by Cruveilhier's experiments of injecting mercury into a vein, after which there was found in the centre of each of the small abscesses a globule of the metal which thus seemed to have been carried in the circulation to the part where it was deposited, and where it excited inflammation passing into suppuration about itself. The pus-globule was supposed to act in the same way as the globule of mercury; being too large to traverse the capillary channels it was arrested there; and similar obstructions taking place in other points of the same organ, a number of separate inflammations, which soon suppurated, and formed the so-called multiple abscesses, were thus established. Another confirmatory fact of the same view was observed in these experiments, viz: that the mercury was arrested almost entirely in the first set of capillaries at which it arrived; if it was injected into tributaries of the portal vein, the abscesses were found in the liver; if into veins of the general system, the abscesses were in the lungs. Pyæmia follows the same law, however, less closely; it is very common to find numerous abscesses in the liver when pus can only have been conveyed from the veins of the general system: on the other hand, that which is carried by the portal vein to the liver often seems to be entirely arrested there. There is no doubt that it is the presence of puriform matter in the blood which gives rise to the phenomena we are considering, but it is not yet fully ascertained whether perfectly-formed pus circulates in the blood, or only a pyogenic fluid, nor how either of these is introduced within the vessels. Before we enter further on these points, we will describe more particularly the formation of the multiple abscesses. M. Lebert, whose observations accord very closely with our own, notices particularly that the parts which are the seat of purulent effusion are truly inflamed; parenchymata, synovial, or serous membranes, if examined at all at an early period, are found in a marked state of inflammatory hyperæmia. This proves that the term secondary depots, sometimes used, is incorrect; the pus is actually generated, not only deposited in the part. The stages of the forming abscess are as follows: "(1.) A local and circumscribed capillary injection, showing little vessels dilated and gorged with a dark red blood, more or less coagulated, in which are seen few globules, and very uniform plasma, but never pus-corpuscles. (2.) In this centre of the vascularization a yellow point begins to be seen, which is nothing more than a drop of pus." The microscope shows in it some well-marked pusglobules, generally without nuclei, and especially many granules, all floating in a pyoblastic serum. (3.) The vascularity declines, the purulent collection increases, infiltrating the tissue, the elements of which are not destroyed. (4.) The secretion of pus continues, and the purulent inflammation is transformed into an abscess, bounded by a margin of red injection, and having its interior, in the case of the larger ones, lined by a soft pyogenic membrane. The larger abscesses have commonly a very irregular form, which results from the fusion of several smaller ones together, as they go on increasing in size. As showing the truly inflammatory character of the pus-secreting process, we may mention that we have found the texture of the cartilage of the knee-joint