DIPHTHERIA, a contagious and (in its severe forms) malignant disease, caused by a specific bacillus and gen erally characterized by the formation of a fibrinous false membrane in the throat. Although previously observed, it was first clearly described in 1826 by M. Breton neap of Tours under the name of "diph terite," as a form of very fatal sore throat occurring chiefly in children. It is now known that most cases of mem branous croup are identical with diph theria.
The period of incubation is usually from two to seven days. The disease be gins by malaise, feeling of chilliness, loss of appetite, headache and more or less fever; soon the throat feels hot and pain ful and the neck is stiff and tender. If seen early, the throat is red and swollen, but a false membrane of yellowish or grayish color quickly appears in spread ing patches, usually first on the tonsils, whence it often spreads to the pillars of the fauces, uvula and back of the throat, and may even extend down the oesopha gus or gullet; extension of the membrane into the nasal cavities is a grave symp tom. There is usually enlargement of the glands at the angle of the jaw, and albuminuria generally occurs at some stage of the disease. Diphtheritic mem brane may be formed on any mucous sur face, or even on a wound; if it extends into the larynx it gives rise to cough and difficulty in breathing. The throat af fection is often accompanied by a low and very dangerous form of fever, with quick, feeble pulse and great and rapid loss of the patient's strength, which is still further reduced by the inability to take food; in other cases, the disease is fatal by paralysis of the heart or by suf focation, due to invasion of the larynx. Invasion of the larynx may necessitate intubation or tracheotomy. After the acute disease is over, the recovery may be delayed by paralytic symptoms of vari ous kinds; or simply by extreme debility with exhaustion and loss of appetite. In the early stages of convalescence there is danger of sudden heart failure upon exertion.
Diphtheria is contagious. It may occur as a complication of scarlet fever, mea sles, and other infectious diseases. All gradations in the intensity of the disease from mild sore throat to septic and gan grenous forms occur. Damp and tem perate climates seem to favor its develop ment. Insanitary conditions favor its oc currence, but the disease may appear under the most favorable hygienic sur roundings.
True diphtheria is now known to be caused by a specific bacillus called bacil lus diphtheria?, or the Klebs-Liiifier ba cillus. Thi: bacillus was first recognized by Klebs in 1883 by microscopical exami nation of diphtheritic membranes, but it was first successfully cultivated by Loftier in 1884. Its causal relation to the dis
ease was not thoroughly established till the investigations of Roux and Yersin in 1888, who demonstrated the existence of a peculiar and intensely poisonous sub stance known as the diphtheria toxin. It is now generally admitted that the Klebs Loffler bacillus is the cause of true diph theria. The diphtheria bacillus is a slender rod characterized especially by ir regularities in shape and staining with aniline dyes.
The ways in which diphtheria bacilli may be conveyed from sick to healthy persons are almost countless. In ordi nary breathing the expired breath con tains no germs, but in speaking and especially in coughing, a fine spray is emitted which may contain the bacilli and thus convey the disease. All sorts of articles, such as handkerchiefs, toys, drinking utensils, furniture, clothing, bed linen and the like, may become contami nated with the bacilli and be the means of spreading the disease. Hence, pre ventive measures, consisting in isolation of the patient till the bacilli have disappeared from the throat and in thorough disinfection, are of the first importance in checking the spread of diphtheria.
The discovery of the diphtheria bacillus has led to the introduction of a new and most successful method of treatment of the disease, known as serum-therapy or the antitoxin treatment. The establish ment of the principles and the introduc tion of this treatment are due especially to Behring of Germany and Roux in Paris. The underlying principle of the treatment is based on the fact that, if a susceptible animal is inoculated first with small and then with increasing doses of the toxin produced by the bacillus, the blood of the animal is found to contain a substance called antitoxin, which has the power of neutralizing or rendering harmless the toxin. In order to obtain large quantities of the healing serum a horse is generally selected for the process of immunization. By proper methods very powerful antitoxins can be obtained. The antitoxin is used not only to cure the disease, but also to render persons in susceptible for a time to the disease. Dr. William H. Welch, of the Johns Hopkins University, in 1895, in an analysis of over 7,000 cases of diphtheria treated by antitoxin found that the fatality was re duced by this treatment by over 50 per cent of the previous death-rates. Since his report this conclusion has been con firmed and even more favorable results have been obtained.