FOCAL INFECTION, a localized area or pocket in the tissues which affords favourable conditions for germs to grow and produce their poisons and from which these germs and poisons may be absorbed into the blood stream and thence carried to different parts of the body. The most common situations for foci of infection to develop are the tonsils, teeth, the bony cavities of the head or sinuses connecting with the nasal passages, certain of the reproductive organs and less often the intestinal tract, appendix, gall bladder and kidneys.
While germs are the direct cause of focal infections, the development, continuation and especially the harm which comes from their source are often attributable to mechanical factors. This being the case, mechanical treatment or surgery, often becomes necessary to effect a cure. Thus, healing of pockets or abscesses in tonsils is often prevented and bacteria and their products forced into the blood or lymph stream because the narrowed openings of dilated crypts become plugged with the products of infection and the walls are held apart by scar tissue, the result of previous attacks of tonsillitis. Mechanical removal of tonsils such as these, is therefore the only rational procedure. Local antiseptic applications or other forms of treatment can be of little value. Strain or repeated injury from mastication on teeth that are out of proper alinement may be the inciting cause of pyorrhea or infection of the enveloping membrane about the teeth. Since the infection in this condition may extend deep into the tissues along the teeth and form pockets plugged with con cretions, cure can best be effected by correcting the contributing mechanical causes.
A properly functioning intestinal tract is rarely a source of infection. If, however, kinks or adhesions develop from localized infection or injury, absorption of bacteria and their poisons is prone to occur. Chronic infections of the appendix and gall bladder which may give rise to disease in distant organs are often directly attributable to kinks, a narrowed lumen from scar tissue or faecal concretions and gall stones. Here again, mechanical or surgical treatment may become necessary.
It has long been recognized that localized infections which are severe and associated with pain, fever and other symptoms, are liable to give rise to disease in remote parts of the body, but that this is also likely to occur from trivial, often symptomless, foci of infection such as occur so commonly in tonsils and in and around teeth, has only recently become apparent. There is still difference of opinion among medical men regarding the relative importance of mild or symptomless focal infections as a cause of diseases in remote parts of the body, but those who have studied the question most thoroughly regard this mode of origin as of common occurrence. Recovery from chronic "rheumatism" even in cases that have perhaps resisted for years the repeated local application of liniments, ointments and other cures is a common occurrence, following the removal of responsible foci. Recurring attacks of arthritis, iritis or other diseases of the eye, appendicitis, ulcer of the stomach, kidney stones and other more vague affections such as slight afternoon rise of temperature. lack of endurance and nervousness, may disappear following the extraction of infected teeth, removal of tonsils, drainage of a sinus or elimination of other responsible focal infection. This new method of treatment is not, however, to be taken as a cure all. Many conditions be too firmly established to be materially benefited; others are not due to focal infection; or the responsible focus may be hard to locate and may easily be missed.
Foci of infection, besides being directly responsible for many diseases, are prone to have deleterious effects in other ways. They interfere with the cure of diseases not attributable to focal infec tion, such as syphilis or tuberculosis. They tend to lower the resistance to intercurrent infections and predispose to complica tions in acute diseases such as scarlet fever and influenza.
The part played by septic foci in the economy of the human organism has been difficult to ascertain. The germs that lurk in focal infections in persons having widely different diseases are often similar and hence were not considered as possible causes of diseases that were so different in their manifestations. The blood of patients does not usually react in a characteristic way with the bacteria isolated from the diseased tissues or organs. The usual injections in animals are without apparent effect. The germs, when grown on artificial mediums, rapidly lose their peculiar infecting powers. It was not until freshly isolated cul tures were injected into the blood stream of animals and the animals, usually seemingly well after injection, were anaesthetized and examined for lesions, that the significance of the germs in foci of infection in their relation to diseases in remote parts of the body, became clearly apparent. These germs, so much alike in appearance, may nevertheless have widely different disease. producing power. Thus, those obtained from foci of infection and the lesions of patients having ulcers of the stomach, produced ulcers of the stomach in the injected animals, or of patients with rheumatism, lesions in the joints, muscles and heart, or if the patient was suffering from certain diseases of the eye, diseases of the eye were prone to occur. Diseases of the heart valves, appendicitis, shingles, inflammation of the gall bladder and gall stones, diseases of the kidney and of the nervous system, infection of the roots of nails, were produced in large part, with germs from infected teeth or tonsils.
In this field, more than in others, the maxim "An ounce of pre vention is worth a pound of cure" holds good. In order, therefore, that the greatest benefits may be derived from this new principle, periodic examinations to learn the state of one's health and the presence or absence of focal infections which may lead to serious disease are strongly indicated. (E. C. R.) Dental Infection.—The bacteria of the mouth usually pro duce no perceptible effect elsewhere in the body until they have penetrated within the vascular structures of the teeth and jaw. They reach these structures by invasion of the tooth pulp (erroneously called nerve) through the medium of deep cavities, or by invasion of the gum tissue by pyorrhea.
Pulp infection follows the vascular channels through the root end and sets up an infection in the bone of that region (root abscess). Root abscesses are either acute or chronic. The chronic root-end infection or abscess leads to serious systemic disease. It is usually painless, and the tooth on which it is located may be entirely comfortable and firm when used for mastication, and may show no inflammation of the overlying gum. This fact was responsible for the failure of dentists and medical practitioners to recognize its existence, before the X-ray was adapted to dental use. Then, it was found that teeth infected through cavities and even teeth from which pulps were removed under supposedly aseptic conditions often developed root infections. This led to a sweeping statement by some dental and medical observers that all pulpless teeth eventually become infected, and that all such teeth should be extracted. These propagandists were soon opposed by others, chiefly dentists, and at the present time the dental profession does not condemn the pulpless tooth as such. The question as to whether a given pulpless tooth is infected or not is determined by diagnostic aids, of which the X-ray is the one most widely used, though interpretation of dental radiographs is not always dependable in the absence of local examination.
Foci of infection may also develop around the roots of teeth subject to pyorrhea. In its later stages this infection invades the soft tissue and bone around the roots of the teeth, producing "pus pockets" from which a certain amount of toxic material is absorbed into the circulation. Infectious foci in the jaws may also occur in other ways, e.g., as a result of leaving broken roots in the bone at the time of extraction; again, root abscesses do not always disappear with the extraction of infected teeth, leav ing "residual infections" in the jaw; or they may result from third molars (wisdom teeth) which have failed to erupt.
Foci of infection may also occur in the tonsils and in bony chambers (sinuses) connected with the nose.