There is a practical side of great importance pertaining to the recognition of the nature of the infectious organism in many cases of suppuration and abscess. For instance, pus which is due to streptococcus invasion indicates a collection which should be freely evacuated and carefully drained. This is also true in essential respects of staphylococcus pus, particularly that due to the streptococcus aureus. Putrid pus from any source requires disinfection and free drainage, the former preferably perhaps by hydrogen dioxide. Pus which is due to the colon bacillus is not often extremely virulent, which accounts for so many cases of appendicitis recovering with or without operation. A collection of this pus needs little more than mere drainage and opportunity for escape. Pus from a recognizable tuberculous source may still contain living tubercle bacilli. This means either that the cavity whence it came should be completely destroyed and eradicated, or else that the margins of the incision or opening through which it has escaped should be so cauterized that infection of a fresh surface is impossible. The same is true of abscesses due to glanders bacilli and to certain cases of suppurating bubo following chancroid, where the whole course of events shows the virulent character of the organisms at fault.
SUPPURATION.
Although it may be possible to produce in certain laboratory experiments metamorphosed material which very closely simulates pus, or, in fact, by injection of chemical irritants, to sometimes imitate the suppurative processes, nevertheless, the student should be brought face to face with the statement, to which for surgical purposes there is no practical exception, that suppuration, i. e., formation of pus, is due to the presence in the tissues of the specific irritants already catalogued and described, and of the peculiar peptonizing or other biochemical changes which bacteria exert upon living animal cells.
Coagulation Necrosis.
—Coagulation necrosis is the term applied to the characteristic changes occurring in the tissue cells when thus attacked, which may be summarized as a fading away of cell outlines, diminution in reaction to reagents, and a merging of cells and intercellular substance. Coagulation necrosis is not the only result of bacterial activity, but may be produced by other causes. Nevertheless, pyogenic bacteria do not exert their deleterious action upon the tissues without occasioning changes included under this term. In an area thus infected, as already described, leukocytes, i. e., phagocytes, are present in increased number for purposes already mentioned. As we approach the centre of activity phagocytes are more numerous than cells, and intercellular barriers completely break down. When bacteria are found in greatest number, there also occurs the greatest phagocytic activity, and there also will be found the evidence of suppuration, i. e., pus. As already indicated, the polynuclear leukocytes are most active in the process of defence. Where coagulation necrosis is most marked there has been the greatest activity of conflict with the greatest death of cells. Around these areas bacteria and cells are found in indiscriminate arrangement. Tissue vitality is impaired by intoxication of the cells by the excretory products of the bacteria, i. e., the so-called ptomains, toxins, etc., and their power of resistance is thus weakened. From the mechanical results of pressure tension around the centre of activity is increased, by which tension vitality is still more impaired and more rapid tissue death occurs. Thus there occurs migration or burrowing of pus; or, to state it more clearly, the tissues break down in front of the advancing destruction, and in the direction of least resistance. This is known as the pointing of pus, which brings it many times to the surface, and often in other and less desirable directions.
Abscess.
—An abscess is a circumscribed collection of pus. The term is used in contradistinction to purulent infiltration, in which the collection is not circumscribed, but is exceedingly diffuse and extends itself in various directions, the amount at any spot being almost inappreciable. Purulent infiltration is regarded as the more serious of the two conditions, as it is more difficult for pus to escape under these circumstances than when it can be evacuated through a single opening. The term phlegmon is one now generally used to indicate a suppurative process, usually of the general character of purulent infiltration rather than of abrupt abscess, but generally employed to include both conditions. The adjective phlegmonous is coupled with the names of other surgical infectious diseases to indicate that it is complicated by suppuration, e. g., phlegmonous erysipelas. Pus is a product of bacterial activity usually formed rapidly rather than otherwise, and abscess formation or phlegmonous activity of any kind is a question of but a few days. Empyema means a collection of pus in a preëxisting cavity.
The significance of this condition is well described in the story of inflammation and suppuration, to paraphrase Sutton, read zoölogically, as though it were the story of a battle: The leukocytes (phagocytes) are the defending army, the vessels its lines of communication, the leukocytes being, in effect, the standing army maintained by every composite organism. When this body is invaded by bacteria or other irritants, information of the invasion is telegraphed by means of the vasomotor nerves, and leukocytes are pushed to the front, reinforcements being rapidly furnished, so that the standing army of white corpuscles may be increased to thirty or forty times the normal standard. In this conflict cells die, and often are eaten by their companions. Frequently the slaughter is so great that the tissues become burdened by the dead bodies of the soldiers in the form of pus, the activity of the cells being proved by the fact that their protoplasm often contains bacilli in various stages of destruction. These dead cells, like the corpses of soldiers who fall in battle, later become hurtful to the organism which, during their lives, it was their duty to protect, for they are fertile sources of septicemia and pyemia. This illustration may seem romantic, but is warranted by the facts.
Around the margin of the site of an acute abscess a barrier is formed by condensation and cell infiltration of the surrounding tissues. This is not a distinct wall nor membrane, yet, nevertheless, serves as a sanitary cordon to confine the mimic conflict within reasonable bounds. This is the zone of real inflammation; within it there are tissue destruction and coagulation necrosis. By virtue of the peptonizing power of the pyogenic organisms the parts involved in this necrosis gradually liquefy the intercellular substance dissolving first. It is this which in the main forms the fluid portion of the pus. Various tissues show widely differing resistance to this softening process. In true glands the interlobular septa seem to break down first, and in this way suppuration extends around the acini or gland lobules, and thus pus may contain masses of easily recognizable size. These masses are ordinarily known as sloughs.
It is by virtue of the so-called lymphoid cells, which are those principally involved in producing the barrier or boundary of the acute abscess as above described, that granulation tissue is formed, which takes up the effort of repair as soon as pus is evacuated. This boundary has no sharp limit, but shades off into healthy surrounding tissues.