DIPHTHERIA (Gr. diPlitheria, a skin, piece of leather, extended in meaning to' corn prise membrane), a contagious and (in its severe forms) malignant disease, caused by a specific bacillus, and generally 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 neau of Tours under the name of Miphtherite,D as a form of very fatal sore throat occurring chiefly in children. It is now known that most cases of membranous croup are identical with diphtheria. The membranous inflammations of the throat occurring sometimes in scarlet fever and other infectious fevers may or may not be true diphtheria, a bacteriological examination being usually necessary to determine this point.
The period of incubation is usually from two to seven days. The disease begins by ma laise, feeling of chilliness, loss of appetite, head ache and more or less fever; soon the throat feels hot and painful 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 spreading 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 oesophagus or gullet; extension of the membrane into the nasal cavities is a grave symptom. There is usually enlargement of the glands at the angle of the jaw, and albumen in the urine generally occurs at some stage of the disease. Diphtheritic membrane may be formed on any mucous surface, or even on a wound; if it extends into the larynx it gives rise to cough and difficulty in breathing. The throat affection is often accompanied by a low and very danger ous form of fever, with quick, feeble 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 suffocation, due to invasion of the larynx. Invasion of the larynx may necessitate incubation or tracheot omy. After the acute disease is over, the re covery may be delayed by paralytic symptoms of various leinds;' or'sithPly by' mitreme debility with exhaustion and loss of appetite. In the early stages of convalescence there is danger of sudden heart failure upon exertion.
Diphtheria is communicable.. It • may occur as a complication of scarlet fever, measles and other communicable diseases. All gradations in the intensity of the disease from mild sore throat to septic and gangrenous forms occur. Damp and temperate climates seem to favor its development. Insanitary conditions favor its
occurrence, but the disease may appear under the most favorable hygienic surroundings. An important mode of its spread is by school chil dren, either infected in a mild form or coming from households where the disease exists. One attack affords little or no protection against re currence. In the treatment of the disease the patient should be isolated and all clothing and other articles which have been in contact with the sick, as well as the discharge, should be disinfected. Local applications to the diseaied parts and means to maintain the strength of the patient were the most valuable therapeutic meas ures before the introduction of the antitoxin treatment.
True diphtheria is now know•to be caused by a specific bacillus called Bacillus diphtheria, or the Klebs-Loffiet bacillus. This bacillus•was first recognized by Klebs in 1883 by microscop, ical examination of diphtheritic membranes, but it was first successfully cultivated by LOffier in 1884. Its causal relation to the disease was not thorqughly established till the• investigations of Roux and Yersin in 1888, who demonstrated the existence of a peculiar and intensely poisonous substance known as the diphtheria toxin. It is now generally admitted that the Klebs-1.45ffier bacillus is the cause of true diphtheria. The diphtheria bacillus is a slender rod characterized especially by irregularities in shape and staining with aniline dyes. It grows best at about the temperature of the human body, and all growth ceases below 20° C. It can be cultivated arti ficially on various media, but best on a mixture of blood serum and beef-broth rendered solid by heating. In a moist condition the bacilli are killed in a few minutes by a temperature of 60° C. They survive for months in a dried condi tion. Exposure to the direct rays of the sun kills the bacilli, in a short time. Guinea-pigs, when inoculated beneath the skin with a small quantity of a pure culture of the virulent diph theria bacillus, die within two to five days with characteristic changes in the body. Skilled bac teriologists can recognize the presence of diph theria bacilli in the throat by microscopical ex amination and the appearances in the cultures within 24 hours or less, but their complete iden tification may require the inoculation of a guinea-pig. Both in human beings and in ani mals the bacilli grow only or mainly locally in the false membrane, the severe constitutional symptoms being due to the absorption of a powerful poison secreted by the bacilli.