Etiology.—As early as 1879 Klebs is said to have observed the presence of a peculiar bacillus in cases of diphtheria. In 1SS3 his observations of the presence of this bacillus in the pseudomembranes from the throats of those dying of epi demic diphtheria were reported and brought to general attention. In 1884 Loeffler published the results of his ob servations. He had found the bacillus present in the great majority of cases diagnosticated as diphtheria, had been able to obtain the bacillus in pure cult ure, had inoculated it upon the abraded mucous membranes of susceptible ani mals and thereby produced pseudomem branous inflammation, often followed by death; he had injected bouillon cultures of the bacillus subcutaneously and had found characteristic lesions after the death of the animals so treated. In 1SSS d'Espine found the bacilli present in fourteen cases of typical diphtheria, and proved them to be absent in 24 cases of mild sore throat, not presenting the clin ical characters of diphtheria. In the same year Roux and Yersin reported that they had found bacilli presenting the characters described by Loeffler in all cases of typical diphtheria. They showed that when inoculated upon the healthy mucous membrane of the trachea of rabbits no effect was produced; but, if the membrane were previously abraded the symptoms of pseudomembranous laryngitis in men followed. Congestion of the mucous membrane, the formation of pseudomembrane, swelling of the glands and cellular tissues of the neck, dyspncea, stridor, and asphyxia. From that time on numerous observations were made in France, Germany, and America, until, in 1891, Welch declared that all the conditions necessary to the demon stration of the specific relation of the Klebs-Loefffer bacillus to diphtheria had been met: (1) its constant presence in cases of true diphtheria, (2) its isolation in pure culture, and (3) the production of all the symptoms of the disease by the inoculation of pure cultures in suscep tible animals. Since that time evidence has been accumulated from many sources, till there can no longer be any doubt that the essential cause of diph theria is the growth and development of this bacillus within the body. The de velopment of the disease must, there fore, be dependent in every case upon the presence and action of the diphtheria bacillus.
The disease is common in all parts of the land. In the cities it is usually en demic, the frequence and virulence of the disease varying from year to year; in rural communities it usually occurs as distinct epidemics, each new outbreak being dependent upon the introduction of the disease from without. It may also occur sporadically. It does not, how ever, in any case arise de novo. Each new case is developed by infection, how ever remote, from some previous one. The infection may be either direct or indirect. Direct infection is undoubt edly most common.
The bacilli are usually present in great numbers in the discharges from the throat or nose of the patients, in the saliva, and in the membranes which may, from time to time, be coughed up. They are not, so far as evidence is had, present in the breath of the patients, but may abound in the air of the room or rooms inhabited by them. The bacilli have
even been reported as present in the urine of patients.
The genitals of every female child who contracts diphtheria in its throat should be examined. Coues (Boston Med. and Surg. Jour., May 12, '9S).
Direct contact with the discharges from the nose or throat of those suffering from diphtheria is most dangerous. Many a physician has fallen victim to diphtheritic infection received by allow ing a child to cough in his face during the process of examination. Kissing the patients may likewise be the means of infection in many cases.
-While severe cases are usually due to the action of virulent bacilli and may, therefore, be especially potent in trans mitting the disease, it is not to be for gotten that apparently mild cases may harbor bacilli just as virulent and just as much to be avoided. As already re marked, the most virulent bacillus Park has met with was derived from a mild case of diphtheria. The cases of virulent pharyngeal diphtheria are most danger ous on account of the quantity of the discharge. Purely laryngeal cases have little or no discharge, and are conse quently less likely to spread the infec tion.
The bacteria may linger in the throat for weeks after the disappearance of all clinical symptoms and the patients con tinue throughout the period to be sources of infection.
In 245 of 405 eases the diphtheria ba cilli disappeared within three days after the complete separation of the false mem brane; in 160 cases the diphtheria bacilli persisted in 103 cases for seven days; in 34 cases for twelve days; in 16 cases for fifteen (lays; in 4 for three weeks; and in 3 for five weeks. In many of these cases the patients were apparently well many days before the infectious agent had disappeared from tbe throat. N. Y.
Health Board (Annual, vol. i, '95).
Indirect infection may cccur by means of the clothing of the patients, the bedding, ca_rpets, wall-paper, draper ies, eating- or drinking- utensils, tongue depressors, swabs, instruments of any kind used upon or about the patient, anything that has come in contact with the infectious discharges. Children's toys or books are especially likely to be contaminated and become means of car rying the germs to others.
In some cases persons who are them selves perfectly healthy, but who have been in contact with diphtheria cases are found to harbor the bacilli in the nose or throat and may be the source of infec tion to others. On several occasions the development of a series of cases of diph theria in a single nursery of the New York Foundling Hospital has led to the examination by cultures of the throats of all children in that nursery, with the result of usually finding two or three who, while apparently healthy, had typ ical germs in their throats.
The isolation of these children would at once break. the succession of cases of diphtheria previously observed. It may also happen that physicians or nurses transmit the germs either by their hands or clothing from one case to another. The frequent occurrence of diphtheria in the families of physicians is sufficient evidence of the need of care.