Elements of Surgery. Robert Liston

was a compound achromatic microscope, with a deep object glass, having one-eighth of an inch focal length.

      In many constitutions, the slightest incited action of the vessels is followed by the formation of pus, and the appearance of a depôt of purulent matter is often the first indication that such action has existed; but in the majority of instances, the deposition of pus is preceded by the usual characters of well-marked inflammatory action. Suppuration occasionally occurs without previous solution of continuity; for pus is frequently contained in the serous and mucous cavities, when no breach of continuity can be discovered, at least we find a fluid not distinguishable from purulent matter; it may be a vitiated secretion, but still it presents the usual characters of pus. But it occurs, generally, when there has been a previous læsion of structure, and in this case its progress is most distinctly marked. In exposed cellular texture, for example, particles of blood are effused; the serum is afterwards absorbed, and the lymph remains; this latter gives transmission to minute vessels which deposit the purulent fluid, whilst others secrete particles of organised matter to form granulations, in order to repair the loss of substance. This process is often unattended with any great degree of constitutional disturbance, because the fibrin effused sets a bound to the pus, and is the provision against its being mixed in large quantities with the blood. In healthy suppuration, the separation of fibrin and pus from the blood in this way seems to have direct relation to each other; and in unhealthy inflammation, when this does not take place, the consequences are mixture of pus with the blood as formerly noticed. In the latter form of suppuration the fibrin, instead of being assimilated to the contiguous mass, is mixed with the pus; hence the proneness to putrefaction of such discharge, and its disposition to coagulate spontaneously when evacuated. This kind of suppuration, being matured generally without thickening of parts, has been sometimes pointed out as suppuration independently of previous inflammatory action.

      After purulent matter has begun to accumulate under the surface, the pressure thereby occasioned produces condensation of the neighbouring cellular tissue, which, along with the previously effused lymph, forms the parietes of the abscess; and in proportion as the matter accumulates, the cavity enlarges by the successive processes of ulceration of portions of its parietes, by continued effusion of lymph, and by farther condensation of the surrounding parts. Thinning of the parietes takes place by ulcerative absorption, particularly towards the surface—or, if that be difficult, towards a mucous outlet—as is exemplified by the bursting into the bowels or bronchiæ of abscess of the liver.

      But in some instances, when no lymph is previously effused, and no cyst is formed, the matter is not confined, but pervades the cellular substance extensively, and is generally followed by more or less sloughing of that tissue, and by great constitutional disturbance. This most frequently occurs in patients of a debilitated habit, in whom the incited action has been so slight as not to cause the effusion of lymph, by which nature usually sets bounds to the suppurating process.

      M. Gendrin advanced the opinion that pus was nothing but transformed blood; but his experiments on frogs are at least doubtful, since Mr. Gulliver, on repeating them, could not by any means induce the process of suppuration in these animals. It has been rendered probable by this gentleman’s observations that suppuration is a sort of proximate analysis of the blood, the fibrin being added to the contiguous parts, as in causing them to swell, forming the cysts of abscesses; the blood globules altered into pus being discharged as useless and excrementitious matter.

      Pure pus is heavier than water, of a yellowish-white colour, somewhat of the consistence of cream. It is very little inclined to putrefaction, less so, perhaps, than any animal fluid not oily. It is composed of globules, and a clear transparent fluid, coagulable, it has been said, by the muriate of ammonia. When a solution of this salt produces any change, it is by rendering the pus more ropy; not coagulation, but a sort of gelatinisation follows. It is said also to be sweet and “mawkish to the taste.”

      In unhealthy pus, such as already noticed, or in vitiated muco-puriform secretion, the colour and consistence are different, and flakes, resembling portions of lymph, are seen floating in it: they consist of fibrin thrown off with the pus, instead of being used for reparation and bounding the extent of the abscess; and by this latter circumstance such fluid is distinguished from the pure or laudable pus. In purulent matter also, especially that of an unhealthy character, the existence of a quantity of sulphureted hydrogen is indicated by the blackening of silver probes, and of various substances applied to the sore. It is necessary to bear in mind, that a matter resembling pus in many particulars, but in reality differing essentially from it, has generally been regarded as true purulent fluid; for it results, from some observations of Mr. Gulliver, that the pulpy matter, so frequently found in the substance of fibrinous clots of the heart and veins, is simply fibrin which has coagulated and passed into the state of softening, which he regards as a very frequent elementary disease. The subject is one of great interest, because it is connected with the theory of suppuration, and tends to modify materially our views on the pathology of the veins.

      The symptoms attendant on suppuration vary much according to the nature of the parts involved. In general, it is accompanied with the subsidence of acute pain and fever; but, in unyielding textures, the increase of swelling, by the formation of purulent matter, is often attended with an aggravation of the symptoms, and with an increase of danger to the structures affected. The pain which accompanies suppuration is dull, and attended with a sensation of fulness and throbbing, and an increase of the tumour; ultimately the parietes of the abscess become absorbed, and the collection, being more superficial, the most careless observer must be convinced of its existence, by the less equivocal signs of fluctuation and pointing. In general, especially when the abscess is deeply seated, a greater or less degree of œdema surrounds it, producing a soft pitting tumour; but not unfrequently, when the degree of excitement is more intense, lymph, instead of serum, is effused, rendering the part more hard and resisting: in such cases it may be difficult to discover the existence of purulent matter, and the tactus eruditus, as it is called, will be found of material service; for, though pus is neither acrid nor corroding, still, if allowed to remain for any long period, much mischief may be caused—the bones may become diseased—muscles and tendons may slough—and the matter may discharge itself, by means of ulceration, into certain cavities and canals, and produce very serious consequences. Of the bad effects produced by the pressure and irritation of extensive and undisturbed collections of purulent matter, every practitioner must have seen numerous examples. Still, through prejudice, erroneously conceived opinions, or servile imitation, the greatest dread seems, with many, to exist of the practice of giving a free exit to the contents of such depôts.

      The symptoms and sensible signs of suppuration are usually preceded by shivering, recurring at intervals, and commonly terminating in profuse perspiration. But this is by no means an unequivocal sign of the occurrence of suppuration; and this process very often takes place without any feeling of rigor.

      The older authors supposed that pus was derived from the solids—or that it was formed by the melting of dead animal matter—or that it was the result of putrefaction; in accordance with which latter opinion, the term pus was given to the fluid; but such opinions have long since been justly exploded. Pus is generally supposed to be separated from the blood by the secreting power of the bloodvessels of an exposed and inflamed part, in consequence of their having assumed a new mode of action. The secretion from exposed surfaces is not at first purulent, but is transparent, serous in fact, and is somewhat of a gelatinous appearance; and it is only, it is said, after exposure to the atmosphere for some time, and when drying, that it presents the appearance of globules. Pus is often formed where the secreting surface has not been exposed to the air; on opening an abscess, the parietes of which had been previously entire and not much attenuated, purulent matter of the usual properties is discharged. It has been asserted that pus globules may be formed independently of any vital action; and that, if the serous fluid be removed immediately after its secretion by a granular surface, and kept in a temperature similar to that of the inflamed part, and be at the same time freely exposed to the air, globules will appear in as short a period as when the secretion is allowed to remain in contact with the sore. Some have also supposed that the mere admission of air into the cellular substance causes suppuration; but this is far from being correct. In chronic purulent depôts, however, the admission of air, by favouring putrefaction probably, often produces most serious