the cavities may be filled with it; their walls and the organs they include may be covered with thick layers of fibrin, which at first is of a pale yellow hue and somewhat transparent, with the consistency of imperfectly coagulated albumen. If death then occur, this hyaline substance quickly becomes granular, and, in consequence of chemical decomposition, is dissolved in the serum; but, if life continue, the characters of the exudation are otherwise altered (p. 42;) which alteration he proceeds to describe as follows:-"The separated serum is gradually absorbed whilst the fibrin floating in it is dissolved. The fibrin which is attached, on the other hand, becomes of a chromeyellow colour, and, if examined under the microscope, is found to consist of a connected exudation of corpuscles, which are found in form twenty-four to thirty hours after the exudation, when the mass is of an orange yellow, and has acquired such consistence as to be stripped off the membrane in slips. *** The exudation-corpuscles are in every respect the same as the lymph-corpuscles; they generally form many superimposed layers, being laid flat one over another, and so constituting membranes which completely resemble the tessellated epithelium when the connecting medium has disappeared, so that the edges of the primarily round corpuscles thrust against each other, and are thus rendered polygonal." Subsequently the cohesion increases, and a more fibrous structure is indicated, and "under the microscope an ever-increasing linear arrangement of the exudation-corpuscles, which are more intimately united at two opposite points in one line, by means of the connecting cyto-blasteina than any where else, is apparent. The original globular cyto-blasts now assume a spindle-like form, and the flat ones continue more flatted as their margins have become more spindleshaped, and in their linear connexion form varicose fibres, at the enlargements of which the nucleus of the exudation-corpuscle continues visible, and either subdivides into several granules, or a new nucleolus is formed within it. Between these now formed cellular fibres there still remains an inter-cellular hyaline substance, so that the masses may be separated mechanically in any direction." (p. 434.)

VALENTIN (a) describes the exudation-corpuscles as “like so many embryonic nuclei -round, granular, and lying tessellated one upon another, whilst their very small interstices contain a transparent gelatin." (p. 215.)

GULLIVER (b) differs from GERBER as to the similarity between the exudation and lymph-corpuscles. "In mammiferous animals," he says," it has always appeared to me that the lymph-globules differ in size, structure, and chemical characters from exudation-globules. The latter are larger, more irregular in size and shape, more spongy or loose in texture than the former;" generally exhibit two or three nuclei when treated with acetic acid, whilst the lymph-globules are only rendered slightly smaller by it. The acid either dissolves or makes remarkably fainter the comparatively thick shell of the exudation-corpuscle, while the lymph-globule becomes more distinct when subjected to the action of the acid." *** The lymph-globules, in fine, in progress of development, may soon become more or less coated with fibrin; but, if examined at an early period, they will be found to resemble in chemical characters the nuclei (nucleoli of VALENTIN) of primary cells." (p. 83.)]

9. Suppuration (Suppuratio, Lat.; Eiterung, Germ.; Suppuration, Fr.) is, when resolution does not ensue, the suitable termination of simple inflammation, and, if that be severe, it appears the natural result; therefore, a fully developed simple inflammation is termed, by some, suppurative inflammation. The pus is secreted through the walls of the capillary vessels, not, however, immediately as such, but is first formed by the changes which the inflammatory exudation undergoes; the coagulated fibrin is gradually converted into pus-globules, which then mix with the Pus is formed of all the components of the blood, the colouring matter excepted, and especially from its albumen and fibrin. If it collect in the cellular tissue, Abscess (Eitergeschwülste, Germ.; Abcès, Fr.) is produced. The process of suppuration is a true secretion, and the vital condition of the organs influences it as well as all other secretions. There is usually no destruction of tissues connected with suppuration. That we often find the remnants of destroyed cellular tissue in pus, or that the skin

serum.

(a) See his "Principal Features in the Development of the Animal Tissues," in WAGNER'S Elements of Physiology, translated by R. WILLIS, M.D.

b) His notes in the Translation of GERBER.

covering the abscess is destroyed, depends on accidental circumstancesin the great distension of the cellular tissue and skin, or in the suppuration, from general or local mischief, passing into Ulceration (Verschwärung, Germ.; Ulceration, Fr.) These remnants of destroyed cellular tissue must not be confounded with the cores (Eiterpropfröpfen, Germ.) so called sloughs, which are found in the midst of the inflamed cellular tissue, at the commencement of suppuration, in the form of white jellylike semi-transparent stringy flocks, which have no trace of organization, are at first firmly connected with the surrounding cellular tissue, but subsequently are thrown out with the pus. These cores are tough concretions of coagulated albumen.

The various opinions relating to the formation of pus may be arranged in two classes:-1. It was supposed that pus was formed and secreted within the vessels of inflamed organs by the peculiar activity of the former. 2. That pus was produced externally to the vessels of the inflamed organs, either in the solid parts in a state of inflammation, or in the effused fluids undergoing a change similar to that of fermentation or putrefaction. According to the former opinion suppuration must be considered as a vital, according to the latter as a chemical, process. The formation of pus as a secretive process first published by SIMPSON (a), more fully discussed by DE HAEN (1756,) and by MORGAN (b), was specially and more accurately proved by HUNTER, by BRUGMANS (c), and by PINEL. Upon the other supposition BOERHAAVE ascribed the formation of pus to the dissolving of the hard parts and the changes which take place in the effused blood; BELL and others to the putrefaction of the serum; GOTTER and QUESNAY, to the change in the coagulable lymph; HOFFMAN and GRASHUIS, to the decay of the fat; and STEWART to putrefaction of the chyle.

The process of the pus formation and the nature of pus, besides the above-mentioned writers, most meritoriously occupied PEARSON (d), HEWSON (e), E. HOME (ƒ), BERZELIUS (g), GRUITHUISEN (h), and have been recently examined with the greatest care; FISCHER (1) has furnished observations on its chemical composition; DONNE (k), GLUGE (1), and VALENTIN (m) have enriched our knowledge of its microscopic elements; GUTERBOCK (n), WOOD (0), BONNET (p), and MANDT (q) have, in a chemical and microscopical view, furnished correct observations, which VOGEL (r) for the most part arranged and increased with the results of his own observation. Compare also VOGEL (8) and E. V. BIBRA (t).

10. The transition of inflammation into suppuration is probable-when the inflammation is active and quickly reaches an acute stage; when the pain is severe, the distension and swelling are considerable, the inflamed part of a lax character, and surrounded with much cellular tissue (1). If the inflammation continue longer than usual, without showing critical movements, if the pain becomes throbbing, the redness and swelling diminish without entirely disappearing, the swelling becomes softer, and the patient has a shiver, then the formation of pus has commenced; the swelling becomes still softer, is elevated in the middle, and sunk at its circumference,

(a) Disput. de re Medicâ, 1722.

Tentamen Medicum de Puris confectione. Edinb. 1756.

(c) Diss. de Puogeniâ. Groenig. 1785. (d) Observations and Experiments on Pus, in Phil. Trans. 1810, p. 294.

(e) In his Experimental Inquiries, Part the Second, containing a description of the Lymphatic System, &c., p. 117. London, 1774. 8vo.

A Dissertation on the Properties of Pus. London. 1788. 4to.

(9) Article "Pus," in his Traité de Chimie, traduit par M. ESSLINGER sur des Manuscrits inédits de l'Auteur et sur la dernière édition Allemande, vol. vii. p. 635. Paris, 1833. 8vo. (A) Naturhistorische Untersuchungen über den Unterschied zwischen Eiter und Schleim. München, 1809.

(1) De Puris indole ejusque à pituitâ discer nendi Methodis. Dorpat. 1836.

(k) Archives générales de Médecine. 1837, Août. (1) CASPER'S Wochenschrift. 1843.

(m) Repertorium für Anatomie und Physiologie, 1837. Part ii. p. 197.

(n) De Pure et Granulatione. Berol., 1837.

De Puris naturá et formatione. Berol., 1837. Mémoire sur la composition et l'absorption du Pus; in Gazette Médicale de Paris, 1837. No. 38.

(9) Ueber den Eiter, den Schleim, und die verschiedenen Ergüsse; in SCHMIDT's Jahrbücher, 1838, No. 19, p. 274.

(r) Physiologisch - pathologische Untersuchungen über Eiter, Eiterung, und die damit verwandten Vorgänge. Erlangen, 1808.

($) In WAGNER's Handwörterbuch der Physiologie, etc.

(t) Chemische Untersuchungen über verschie dene Eiterarten und einige andere krankhafte Substanzen. Berlin, 1842.

and on touching it fluctuation (Schwappung, Germ.) is felt. In order to be assured of this, the fingers may be pressed alternately upon the swelling, or, what is preferable, the finger or the flat hand may be laid on the side of the swelling, while this is gently tapped with the fingers upon the other, by which the undulations of the pus are communicated to the hand. The skin becomes transparent at the most elevated part, and the pus is seen through it; finally, the skin breaks by the process of continued absorption, and the pus is discharged. If the parts covering the abscess are unyielding, an extension of the suppuration takes place in various directions before it makes its way out (2). If the inflammation be slight, it often continues a long time without exhibiting any disposition to break. It is often very difficult to distinguish the transition to suppuration in inflammation of deeply situated or in internal organs. The usual appearances are-the symptoms of inflammation subside without crisis, the part does not return to its natural functions; it feels to the patient heavy, oppres sive, or cold; he has frequent shiverings; the appearances of hectic fever set in, burning heat of the hands and soles of the feet, especially after eating, circumscribed redness of the cheeks, emaciation, night-sweats, purgings, and so on. Deep-seated fluctuation is felt, or the surface of the part exhibits an oedematous swelling. The symptoms of hectic fever accompany every considerable suppuration, and it is probable that this must be ascribed partly to the loss of the albumen and fibrin of the blood, and partly to the absorption of pus.

The circumscription of the pus in the cavity of the abscess depends upon the effusion and coagulation of the plastic lymph, which occur during inflammation, whereby a cavity with smooth walls is produced, in which the capillary vessels are very strongly developed, so that the pus is shut off from the other cellular tissue, and its spreading from cell to cell is prevented. In cases in which the inflammation is not connected with plastic exudation this circumscription of the abscess does not take place; for instance, in many erysipelatous inflammations. If suppuration occur on the surface of serous membranes, there must always be first produced a considerable development of vessels. In structures which are very highly vascular, suppuration occurs more rapidly. The walls of the abscess must be considered as secreting and absorbing surfaces. In the resorption of pus, (by the veins and lymphatic vessels,) it is mixed with the blood and separated from it by the colatories of the body, specially the lungs and kidneys, or is deposited in the tissue of parts (metastatic abscesses;) it is, however, undetermined whether the pus is deposited as such or is produced by the after-changes which commonly occur in the inflammatory exudation (VOGEL.) As the pus-corpuscles are larger than those of the blood, they cannot pass through the capillary vessels, and therefore only the serum of the pus is absorbed, or the pus-corpuscles are broken down, and can then also be absorbed. We must not confound with this the entry of pus into a torn vein, or its formation by phlebitis in the vein and its further passage onwards with the blood. In regard to the operation of absorbed pus, BONNET supposes that the absorption of good, cream-like pus, which has not been changed by the action of the air, will not produce any peculiar symptoms, because with it nothing enters into the blood but what is natural to it; but, if in depraved putrid pus hydrosulphate of ammonia be developed with a residue of ammonia, and be absorbed with the serum or pus, a septic poison is introduced into the blood, the presence of which has been ascertained by BONNET in the blood, and its separation in the urine.

[(1) The true inflammatory disposition and action," says HUNTER, "almost immediately ceases upon the commencement of suppuration; and, although the vessels may be nearly in the same state, yet they are in a much more quiescent state than before, and have acquired a new mode of action." *** And he asserts, as an invariable fact, that no suppuration takes place which is not preceded by inflammation; that is, no pus is formed but in consequence of it."***"The immediate state of parts which may be called the immediate cause of suppuration, I conceive to be such as cannot carry on its usual functions of life, and which state of parts I have called the state of imperfection, let the cause of that state be what it will; we have shown that irritation

simply is not always sufficient, it often only brings on the adhesive stage, which is in most cases intended to prevent the suppurative." (p. 372.) " In spontaneous suppurations, one, two, three, or more parts of the inflammation lose the power of resolution, and assume exactly the same disposition with those of an exposed surface, or a surface in contact with an extraneous body. If it is in the cellular membrane that this disposition takes place, or in the investing membranes of circumscribed cavities, their vessels now begin to alter their disposition and mode of action, and continue changing till they gradually form themselves to that state which fits them to form pus; so that the effect or discharge is gradually changing from coagulating lymph to pus: hence we commonly find in abscesses both coagulating lymph and pus, and the earlier they are opened, the greater is the proportion of the former." (p. 378.)

“Should the exudation become purulent, this gelatin (viz. that which is interstitial to the corpuscles) acquires fluidity," says VALENTIN," and the plus globules then swim in the liquor puris, sink tessellated to the bottom, and surround themselves with cells, which subsequently undergo tranformation in accordance with certain laws into exudation fibres or exudation membranes." (pp. 215, 216.)

"This (suppurative) inflammation has symptoms common to inflammation in general; but," says HUNTER, "it has these in a greater degree than the inflammation leading to it, and has also some symptoms peculiar to itself: *** it gives as much as possible the idea of simple pain without having a relation to any other mode of sensation: **the pain is increased at the time of the dilating of the arteries, which gives the sensation called throbbing, *** perhaps one of the best characteristics of this species of inflammation. [This observation, as already noticed, (p. 23,) is incorrect.-J. F. S.] When the inflammation is moving from the adhesive state to the suppurative, the pain is considerably increased (and which would seem to be the extent of this operation in the part;) but when suppuration has taken place the pain in some degree subsides. *** The redness that took place in the adhesive stage is now increased, and is of a pale scarlet: this is the true arterial colour, and is to be accounted a constant symptom, as we find it in all internal inflammations, when at any time exposed, as well as in those that are external." The dilatation of the old vessels, and the formation of new ones, which had occurred in the first or adhesive state of the inflammation," are here carried still further in the surrounding parts, which do not suppurate, and constitute two other causes of this redness being increased by the vessels becoming more numerous, and the red part of the blood being pushed more forward into many vessels, where only the serum and coagulating lymph went before. The part which was firm, hard, and swelled, in the first stage, now becomes still more swelled by the greater dilatation of the vessels and greater quantity of extravasated coagulating lymph thrown out in order to secure the adhesions. The oedematous swelling surrounding the adhesive gradually spreads into the neighbouring parts. *** There is a certain period in the inflammation, when the suppurative disposition takes place, which is discovered by new symptoms taking place in the constitution, viz. shivering.” (p. 377-79.)

"The vessels are but little changed from the adhesive state at the commencement of the suppurative disposition; so that they still retain much of the form they had acquired by the first state, the discharge being at the beginning little more than coagulating lymph, mixed with some serum. This is scarcely different from the adhesive stage of the inflammation; but, as the inflammatory disposition subsides, the new disposition is every instant of time altering those vessels to their suppurative state; the discharge is also varying and changing from a species of extravasation to a new formed matter peculiar to suppuration; this matter is a remove further from the nature of the blood, and becomes more and more of the nature of the pus; it becomes whiter and whiter, losing more and more of the yellow and green which it is apt to give the linen that is stained with it in its first stages, and in consistence more and more viscid or creamy." (p. 415.)

JOHN HUNTER describes that as "an abscess in this part," i. e. when "collections of matter are found in parts where not formed, more especially in the deeper-seated ones, the matter moving from the seat where it was formed to some more depending part, or, having met with some obstruction in its course, it takes another direction;" whilst abscesses which are commonly formed where matter is found, especially the more superficial ones, may be justly called abscesses of this part. (p. 510.) Suppuration takes place much more readily in internal canals than internal cavities; *** more readily upon the surface of canals than in either the cellular or investing membrane. The same cause which would produce a suppuration in the first parts (the canals) would only produce the adhesive in the other (the cavities.)" (p. 377.)

"The cavity (of the abscess,)" observes TRAVERS," is surrounded by an effusion, and lined by a pellicle of lymph (pyogenic membrane,) whence the pus is furnished." (p. 125.) "The aspect of the suppurating membrane varies to such extent as scarcely to exhibit, in some circumstances and situations, the granular form, e. g. upon the walls of abscesses, and upon the free surfaces of mucous and serous membranes; but the fibrinous bed and the capillary loop of new formation, and a corresponding alteration of the pus-secreting surface from its normal state will always be detected upon careful examination, being essential elements of the suppurative process." (p. 111.) "A section of an abscess, from circumference to centre, presents the condensation of the wall by the deposit occupying the cells of the cellular membrane, the secreting membrane, the semi-solid flakes of lymph, and the collection of pus forming its contents; the arrangement, appearance, and proportion of each varying according to the stage of the suppuration." (p. 125.)

(2) Of the circumstances upon which depends the determination of abscess to the surface, the following very interesting account is given by JOHN HUNTER:-" An internal pressure, produced by an extraneous body, acts equally on every side of the surrounding parts, and, therefore, every part being pressed alike, ought from this cause alone to produce absorption of the surrounding parts equally on all sides, supposing the parts themselves similar in structure, or, which is the same, equally susceptible of being absorbed; but we find that one side only of the surrounding living parts is susceptible of this irritation: therefore, one side only is absorbed; and this is always the side which is next to the external surface of the body. *** From this cause we find abscesses, &c., whose seat is in or near the centre of a part, readily determined to the surface on the one side, and not on the other; and, whenever the lead is once taken, it immediately goes on." (p. 448.) He also observes:-"We find that the absorption of whole parts more readily takes place, to allow an extraneous substance to pass out of the body than it will to allow one to pass in. Thus we see that the slight pressure produced by matter on the inside of an abscess has a great effect, and the matter is brought much faster to the skin (although very deep) than it would by the same quantity of pressure applied from without; and, indeed, so slight a pressure from without would rather tend to have an opposite effect, namely, that of thickening. The reason of this is evident: one is, a readiness in the parts to be freed from a disease already existing; the other is a backwardness in the parts to admit a disease. This principle, therefore, in the animal economy produces one of the most curious phenomena in the whole process of ulceration, viz. the susceptibility which the parts lying between an extraneous body and the skin have to ulcerate, while all the other side of the abscess is not irritated to ulceration; and the necessity there is that it should be so must be very striking; for, if ulceration went on equally on all sides of an abscess, it must increase to an enormous size, and too great a quantity of our solids must necessarily be destroyed." (p. 449.)

But mere pressure is not, according to HUNTER'S views, sufficient for bringing the contents of an abscess to the surface; there is an operation," says he, " totally distinct, and this is a relaxing and elongating process, carried on between the abscess and the skin, and at those parts only where the matter appears to point. It is possible that this relaxing, elongating, or weakening process may arise, in some degree, from the absorption of the interior parts; but there is certainly something more, for the skin that covers an abscess is always looser than a part that gives way from mere mechanical distension, excepting the increase of the abscess is very rapid." (p. 460.) TRAVERS, in commenting upon this point, observes :-" Whether the tendency of matter to the nearest surface, external or internal, the outer or inner integument, as the case may be, is due to the more yielding structure of parts in the direction of the nearest surface or to the operation of a physical law, as the increased amount of pressure from the increased area of the summit over the base, I cannot determine." (p. 188.)]

11. Pure good pus (1) is an opake, tolerably consistent, yellowish white fluid, with a peculiar smell when fresh, which it loses on cooling, and of a sweetish taste, specifically heavier than water, (spec. grav. 1,030,) (2), not readily subject to putrefaction (3); reacts in its fresh state as an alkali; but, after a time is neutral or acid, probably because during its decomposition it forms acetic acid; and under the microscope is seen to consist of fluid parts and globules (4) which can be separated by straining (5); but very frequently this separation occurs spontaneously if the pus be left alone.