of blood. In one experiment the blood, which had pus (healthy) added to it, coagulated in six minutes; while that which was left by itself re

Fig. 18. a. Natural appearance of pus-corpuscles. b. Appearance after application of acetic acid. Fig. 19. Pus-corpuscles, magnified 400 diameters.

Fig. 20. Healthy pus-cells.

Figs. 21, 22, 23. Various forms of pus-cell from phlebitis and pyæmia.

quired twelve. The pus must, of course, act upon the fibrin; but of the nature of the change, we have no knowledge. The following analysis, by Dr. Wright, exhibits the main features of the chemical constitution of pus very well. They apply, of course, to pus as a whole, not to the serum only. The large quantity of fat in pus is remarkable, as well as the amount of albumen-the latter sometimes exceeding that contained in the liquor sanguinis. This is probably to be explained by the dissolution of some of the red globules, and the blending of their albuminous globulin with the exudation that yields the pus.

Fig. 24.

In various unhealthy states of the system pus is formed, which differs in several respects from that which we have now described. Mucin, the peculiar principle of mucus, may be more or less abundantly dissolved in the serum, which may be recognized by the coagulation produced by acetic acid and alum. Small fibrinous flakes, epithelial particles, cholesterin scales, and prisms of triple phosphate may also be mingled with it, as well as varying quantities of free oil. The pus-globules are in such cases often ill-shaped, feebly formed, conveying the idea of very defective formative power; the quantity of granular matter mingled with them is much increased.

One variety of pus has been called ichor, and is especially distinguished by the paucity of its corpuscles, which, indeed, Vogel says, are absent when it is perfectly pure. Its color is reddish, or brownish red, it is alkaline, and contains a considerable quantity of albumen. Its presence indicates an exceedingly depressed state of the vital formative power. Certain unhealthy kinds of pus, which Rokitansky comprises under the term (Jauche) sanies, are especially distinguished by their corrosive action upon the tissues, which he contrasts particularly with the bland quality of healthy pus. Their appearance is not at all constantly different from that of the normal fluid, but they are apt to be thinner, more tinged by hæmatin, of an offensive, or ammoniacal smell, and to communicate a sensation of pricking or itching to the finger when applied to them. Their corpuscles are stunted, and their developments are variously altered, apparently by the "gnawing" action of the serum in which they float. It seems to us very questionable, whether the dissolving action which pus is said to exert on pieces of dead flesh, belongs at all to it in a healthy and fresh state, and whether it does not really depend on the generation of acids within itself, in consequence of decomposition. Purulent effusions may degenerate into a semi-fluid amorphous mass, the corpuscles breaking up, and the serum undergoing chemical changes, often of a putrefactive kind. They may also undergo fatty degeneration, calcareous salts being liberated, or deposited at the same time. Either of these two changes being premised, it is possible that a purulent collection may be absorbed, but it is only too probable that in the former case the result will be a fatal contamination of the blood by the decomposing matters taken up into it. Apparent temporary absorption may be easily produced by means which, creating a considerable demand for fluid, withdraw the serum

from the pus-corpuscles; but as these retain their vitality, they soon attract a fresh quantity of blastema from the blood, and the abscess remains undiminished. This persistent vitality of the organized corpuscles of a fluid which is regarded as effete in the highest degree, and incapable of any further development, is certainly remarkable; one would rather have expected that they would have disintegrated rapidly. Pus may be confounded with some other fluid, and the distinction is sometimes only to be made out by careful microscopical examination. What we have said respecting softened fibrin, will show that a fluid having this origin may approach very closely to the purulent product of inflammation; so much so, that it may be doubted whether it be not in part identical with it. It has happened several times, that a quantity of desquamated epithelium, the particles being partly entire, partly broken up, has been mistaken for a collection of pus. Vogel records an instance of this in the pelvis of the kidney of a person who died with empyema. The pus-like fluid accumulated in the urinary passages, was deemed convincing proof that absorption of the thoracic effusion had been taking place with subsequent elimination of the same by the kidneys. The microscope, however, showed that the whitish-yellow, thick, creamy fluid which had been considered as pus by all who saw it, consisted entirely of epithelial debris. We shall presently describe mucus, and will then point out wherein we believe it to differ from pus. A caution is necessary against a very possible error which even practised observers have committed, viz: that of mistaking the colorless corpuscles of the blood for pus-globules. The two bodies are very much alike, but the blood-corpuscle is somewhat smaller, generally more finely granular, and with rather less definite contour. The interior nuclei of, both are identical.

The granule-cell, exudation globule, or glomerulus, which was first described by Gluge, and called by him the compound inflammatory

Fig. 25.

2

Glomeruli and granulous cells.

(1) From ovarian cyst.

(2) From cancer of breast.

(3) From inflamed lung.

(4) From inflamed pia mater.

(5) From a case of tuberculous meningitis.

The opaque cells are the glomeruli, the more simply granulous are the granular cells.

globule, is very frequently present in exudation, and is, speaking generally, a valuable sign of the existence of the inflammatory process, but

not an infallible one. The granule-cell is usually of large size, from 400-inch, mostly spherical, but often oblong, or of irregular shape. By transmitted light they appear dark, on account of their opacity; by direct, of a dead white. Their structure will be best understood from the account of their development. Our own observation exactly accords with that of Vogel, who states that there are first formed in the blastema nucleated granular cells, which gradually fill themselves with the peculiar opaque glistening granules characteristic of these corpuscles, until at last the nucleus is entirely obscured, and the originally smooth-cell membrane becomes rugged, the granular cell appearing as an agglomeration of granules. Subsequently the cell-wall vanishes, the granules separate from each other, probably on account of the dissolution of the uniting substance, and the corpuscle breaks up into a loose heap of oily-looking granules. Vogel says that caustic potash and ether sometimes, but not always, dissolve these granules; Rokitansky regards them as of fatty nature, and considers the process of granule-cell formation as one of fatty degeneration of pre-existing cells. He says that granule-cells do not form in blastemata devoid of cells, and that any cell may undergo this transformation, a cancer-cell, a pus-cell, as well as the cells that form in exudations. There is no doubt that blastemal exudations, devoid of cells, often break up into collections of the fatty-looking granules, and that they may assume this form from a very early period; as, for instance, in the coating of the vessels in the gray matter in meningitis. Corpuscles also, quite indistinguishable from granule-cells, occur in lungs that bear no trace of having ever been inflamed, and this in considerable numbers. We do not think, therefore, that Rokitansky's view of the nature of the process is quite correct, but are inclined to believe that, generally, where blastemal exudation has been poured out in greater quantity than is necessary for the nutrition of the tissue, it may undergo such a change, as that its oil, in combination with a part of its albumen, separates in the form of glistening granules, while the remainder undergoes absorption, or is otherwise consumed. The granules appear to be attracted towards the interior of existing cells; we have distinctly seen them coating the outside of a cell. One of the causes of the different size of the granule-cell depends on the circumstance that cells of very different magnitude, and cells in very different stages of growth, may be the seat of their deposition. Between the suppurating process and that which forms granule-cells, a wide separation exists; the former, as we have seen, gives rise to a fluid essentially effete, rarely, with diffi culty, or with peril, capable of being absorbed; the latter involves no such deteriorating alteration of the blastema; its occurrence, on the contrary, is eminently favorable to reabsorption of an exuded mass. It is to be remarked, in conclusion, that a very abundant cell-growth commonly takes place in exudations, many particles of which are correctly denominated granular cells. These are not to be mistaken in descriptions for the granule-cells, into which they often undergo metamorphosis. The similarity of the name is unfortunate, but the subjoined sketch will make the distinction between the two very apparent. The last inflammatory product which we have to notice is mucus.

Speaking correctly, it is only unhealthy mucus which comes under this head; for it is perfectly clear that several internal membranes secrete a mucous fluid. The distinction between this and the morbid product is tolerably precise, and easy to be ascertained. The former is a tenacious, clear fluid, containing only some admixture of the epithelium of the membrane producing it, and having no special corpuscles of its own. The latter is loaded with corpuscles, identical with those of pus, together with a varying quantity of epithelial debris. Between such mucus and pus it is evident that a close analogy subsists. Mucus may be distinguished, like pus, into a fluid, the liquor muci, and corpuscles. The liquor muci, as we find it in the secretion of a membrane which has been subjected to moderate irritation, is a transparent, tenacious, more or less stringy fluid, of alkaline reaction, and more or less saline taste. The addition of acetic acid, or any weak acid, produces a kind of coagulation, and the formation of a granular precipitate, which Simon states is the mucine, the principal constituent of the fluid. This is held in solution by means of an alkali, and consequently falls on the latter being taken up by an acid. Not much is known of this substance, except that it is a protein compound. Albumen or fibrin, treated with liquor potassæ, forms a transparent, viscous mass, having much resemblance to its solution. The proper corpuscles of morbid mucus are, as we are fully persuaded, and as the best observers state, quite identical with those of pus. They are usually mingled with epithelial particles, in very various stages of their formation, from a simple nucleus up to a complete cell. It is only in cases of prolonged and rather intense inflammation that traces of epithelium are wanting, and the so-called mucous corpuscles are crowded together, and seem to load the fluid. In mucus expectorated by persons of very depressed powers, the cor

puscles may be seen feebly formed, like those of pus secreted under similar circumstances; the granular contents of the cell are deficient, and allow the composite nuclei to be distinctly seen. It is often very observable how the tenacious fluid, in which the corpuscles are entangled, in consequence of being dragged in one direction, produces an alteration of their shape; they thus become oval, or even staff-shaped. Granulous and oily matter is commonly diffused through the liquor muci, just as it is through that of pus. It is manifest, from what has been stated, that the difference between mucus and pus consists essentially in the different nature of the fluids, not in that of their corpuscles. Both are exudations; but the one is poured out directly from the blood vessels, as