We now proceed to notice the origin and-mode of propagation of these two diseases, beginning with typhus. There is undoubted evidence that all the forms of continued fever arc contagious, and it may now be regarded as an established fact, from the inves tigations of Dr. Jenner, that one species of fever cannot generate another, but that each is produced solely by its like; that typhus, for example, always propagates typhus, and never any other form of fever, as typhoid or relapsing fever. Some persons may, by some peculiarity of constitution, be able to resist the action of the poison, while others are peculiarly suseeptibie to it. An attack of fever generally exerts a certain amount of protective power against another attack of the same kind of fever; and habit has a good deal of power in fortifying the system against contagion, just as confirmed drunk ards or opium-eaters can with impunity swallow doses of their respective poisons which would prove highly dangerous to a novice. " Upon this principle," says Dr. Watson, "has been explained the comparative immunity from contagious diseases, under like circumstances of exposure, of medical practitioners and nurses; of the keepers of filthy lodging-houses, while the new-coming inmates suffer; and even of prisoners, who, with out having had the disease themselves, may nevertheless carry forth and communicate the infection, as is said to have happened at the celebrated ' black assizes' at Oxford, and again at the Old Bailey in the year 1750."—Lectures on the Principles and Practice of Physic, 4th ed., vol. ii. p. 829. Whether typhus can be generated de novo by great over crowding and vitiation of air, by the organic impurities emanating from the respiratory and other functions, is still a disputed question. The conditions essential to its propa gation are (1) overcrowding, combined with deficient ventilation; (2) personal filth, and clothes saturated with cutaneous exhalations; and (3) an impaired condition of the sys tem, such as may result from insufficient food, scurvy, and any other debilitatingcauses. The patient is most dangerous as a focus of infection after the end of the first week to the period of convalescence, the peculiar odor from the skin and lungs being then the strongest. If the poison he very concentrated, the disease may be caught by exposure to it for only a few minutes. The infected person may actually be conscious when the poison is taken in. Dr. Banks of Dublin, in an excellent lecture which he delivered on April 24, 1866, in the theater of the Richmond hospital," On the Origin and Classification of Fevers," states that this happened in his own case, while examining the chest of a person laboring under the disease. " The patient," he observes, " was seized with cough, and I was so placed that I must have inhaled his breath. The odor was pecu liar and intolerably offensive. I was certain that I had imbibed the poison; and after a latent period of three days, I exhibited the usual train of symptoms which usher in typhus of the severest form." The most common latent period is nine days.
From the investigations of various physicians, among whom Dr. William Budd deserves especial notice, it appears that the living human body is the soil in which the specific poison of typhoid fever breeds and multiplies. The origin of the disease is unknown, but the poison is communicated or contained in the diarrhea' discharges which issue from the diseased intestine. These discharges, as they dry up, preserve the germs of the disease; and if, through atmospheric or other agencies, these germs enter the living body, they communicate the disease, and diarrhea soon commences. As the evacuations contain the specific virus of typhoid fever, the disease may be propagated among healthy persons (1) by percolation through the soil into the wells which supply drinking-water; (2) or by issuing, through defects in the sewers, into the air which is inspired; or (3) by exhalation through the apertures of small ill-trapped •water-closets or privies, which are at once the receptacles of the discharges from the sick, and the daily resort of the healthy. The atmosphere thus infected with the poison is far more dan
gerous than that immediately surrounding a fever-patient.
For a knowledge of the means of checking the spread of typhoid fever, society is deeply indebted to Dr. Budd's researches; and provided these means are thoroughly and efficiently carried out., it is believed by many of the most eminent physicians that the recurrence of this disease might be entirely prevented. In order to judge of the extent of the infection to be destroyed, there are two points to be considered—viz., first, the amount and duration of the intestinal discharge in each ease; and secondly, the number of cases actually occurring. With regard to the first point, the diarrhea lasts on an average 15 days. With regard to the second point, the reports of the registrar-general show that at least 100,000 to 150,000 cases of typhoid fever occur annually in England alone; or, in Dr. Budd's emphatic words, " every year in England, more than 100,000 human intestines, diseased in the way already described, continue each, for the space of a fortnight or thereabouts, to discharge upon the ground floods of liquid charged with matters on which the specific poison of a communicable disease has set its most specific mark." He suggests the-following details of procedure, which should be invariably attended to as soon as this disease appears: 1. All discharges from the fever-patient should be received, on their issue from the body, into vessels containing a concentrated. solution of chloride of zinc. 2. Two ounces of a caustic solution of chloride of zinc should be put in the night stool on each occasion before it is used by the fever-patient. 3. All tainted bed or body linen should immediately on its removal be placed in water strongly impregnated with the same agent. 4. The water-closet should be flooded several times a day with a strong solution of chloride of zinc; and some chloride of lime should also lie placed there, to serve as a source of chlorine in the gaseous form. 5. So long as lasts, the water-closet should be used exclusively as a receptacle for the discharges from the sick. For further details as to the various precautions to be taken with a view of checking the spread of this and other epidemic diseases, the reader is referred to Mr. Simon's "General Memorandum," published (in 1860) in his Third Report on the Public Health in England.
Although typhoid is conta7ious, Dr. Jenner holds that it is " infinitely less so than typhus." Hence in typhus a large room should, if possible, be selected for the patient, and the air should be kept fresh by having a window or door, or both, open. Curtains, carpets, and all superfluous furniture should be removed, and the body of the patient should lie kept as clean as possible by ablution, and his sheetsand night shirt frequently changed; the latter being at once plunged into water containing chloride of zinc. As the susceptibility to the disease diminishes with the advance of life, middle-aged attend ants should be selected: and all who approach the sick-bed should avoid as far as possi ble inhaling the patient's breath or the emanations from his skin. Friends occasionally visiting the patient should do so after a meal and a glass of wine or ale. Formerly it was the practice to distribute cases of typhus fever in the general wards of hospitals— the rule being to distribute them scantily among the general patients. This practice came to be looked on as unadvisable; and now each hospital is provided with its fever house to which cases of typhus are strictly limited.