Other indications of the presence of pus are a well-marked leukocytosis, coupled with the iodine reaction indicating the existence of glycogen in the blood, the presence of indican in the urine, and the positive results frequently obtained by making cultures from the blood. When pyogenic bacteria are found in the blood the inference is very plain, and both treatment and prognosis are influenced. In such a case the introduction into the blood of an antiseptic such as Credé’s soluble metallic silver or of the antistreptococcus serum, is plainly indicated. The absence of bacteria from the blood, under these circumstances, does not disprove the presence of pus, but their presence gives a very serious character to the disease, and should lead to a most guarded prognosis. Invasion of the blood by staphylococci is nearly twice as serious as when streptococci gain entrance. Suppuration of the bones and of the tendon sheaths is liable to produce such invasion.

The other disturbance with which suppuration is so often complicated is septic infection. In fact it may be questioned whether pyrexia is not an expression of this condition. Any collection of pus, no matter how small, may show signs of septic infection; and, on the other hand, large collections may be formed without serious septic symptoms—in other words, suppuration and expressions of septic infection may be blended in almost every conceivable way. Sepsis as a distinct condition will be described in another chapter.

It is important to summarize what may become of pus when once it has formed and is not promptly evacuated. Pus when long present may be—

A. The possibility of the absorption of pus, or, what is equivalent to it, its spontaneous disappearance, has been mentioned. While it does not usually take this course, it may thus disappear; as, for instance, in the anterior chamber of the eye in cases of hypopyon, or in various other localities, particularly when present only in small amounts. The absorption of pus is purely a matter, as far as we know, of phagocytic activity plus the power of the tissues to take up various fluids.

B. Encapsulation.—This occurs only when pus has been present for some time and when the virulence of the pyogenic organisms is not intense. We may get encapsulation of pus in any part of the body, the most typical illustration naturally being within the bones. Around the purulent focus, as around any other irritating foreign body, the capsule is formed by condensation of surrounding tissue. This is the way in which most cold abscesses with their limiting membranes are produced, those produced by tubercle bacilli having slight irritating properties. Inasmuch, then, as the biological activity in such a focus is small, there is time for such encapsulation; while by the membrane thus formed, or the sanitary cordon, already referred to, protection is afforded to the surrounding tissues. In such a collection fresh infection may incite acute disturbances again, and many abscesses which thus lie latent for a considerable length of time are fanned, as it were, into a conflagration, when a new and acute inflammation is produced.

C. Of the various metamorphoses and chemical changes that occur in that which was originally pus, the caseous and the calcific are the most common. These also are connected largely with the tuberculous process, although calcareous particles are found in the pus of actinomycosis. Under their respective heads these degenerations will be more particularly described.

Certain names have been given to collections of pus in different localities or under peculiar circumstances. A collection of pus in the anterior chamber of the eye is known as hypopyon; when in any preëxisting cavity, it is known as empyema of that cavity, the distinction between empyema and abscess being that “abscess” means a circumscribed collection where previously there was no cavity, while “empyema” implies a normal cavity, without respect to size or location, filled with this abnormal fluid. The term empyema, when not used in connection with some particular cavity, is understood to refer to a collection of pus in the pleural cavity. Other names also are used which are particulate and distinctive; in these the prefix pyo is used while the suffix indicates the part involved; thus we have pyothorax, pyopericardium, pyarthrosis, etc.

SINUS AND FISTULA.

These are terms applied to more or less tubular channels abnormally connecting various parts of the body, or connecting some cavity with the surface of the body in a way anatomically quite abnormal. Or they may be regarded as tubular ulcers, or ulcerated tunnels, connecting as above. A more exact distinction between the two terms would imply that a sinus connects the surface with some deeper portion where a cavity is not normally present—i. e., with a focus of disease—whereas a fistula properly refers to a tubular passage connecting natural or preëxisting cavities in an abnormal manner. Thus we speak of buccal, rectal, vesicovaginal fistulas, etc., whereas a passage leading down to an old abscess or to a focus of disease in bone, for instance, is properly referred to as a sinus. It is possible for the margins of a fistula to become more or less cicatrized and cease to be ulcerous, whereas the entire track of a sinus is practically a continuous ulcer, only tubular in arrangement.