The other means of dissemination are polluted soil, food and drink, particularly milk and water. The mode in which polluted soil acts is by contamination of water-supply. Exhalation is not regarded as a channel of communication. The researches of Majors Firth and Horrocks prove that dust, flies and clothing may convey the germs. Another way in which food becomes the medium of conveyance is by the contamination of oysters and other shellfish with sewage containing typhoid bacilli. This has been abundantly proved by investigations in Great Britain, Amer ica and France. Uncooked vegetables, such as lettuce and celery, may convey the disease in a similar way. The most familiar and important medium, however, is water. It may operate directly as drinking water or indirectly by contaminating vessels used for holding other liquids, such as milk cans. Outbreaks have been traced to ginger-beer and ice-creams. Water sources become con taminated directly by the inflow of drains or the deposit of ex cretal matter ; indirectly, and more frequently, by the leakage of sewage into wells or by heavy rains which wash sewage matter and night-soil from ditches and the surface of the land into springs and watercourses. Water may further be contaminated in the mains by leakage, in domestic cisterns and in pipes by suction.
Typhoid fever is more or less endemic and liable to epidemic outbreaks all over the world. It has undergone marked and progressive diminution in many countries coincidently with improved sanitation, particularly in regard to drainage and water-supply. The case of Munich is so instructive that it de serves special mention. For many years typhoid was excessively prevalent in that city. The prevalence was continuous, but aggra vated by large epidemic waves, extending over several years. These gradually decreased in magnitude, and ceased towards the end of 1880. Subsequently the prevalence still further diminished, the average annual mortality per million falling from 2,024 in 1851-1860, 1,478 in 1861-1870 and 1,167 in 1871-1880 to 160 in 1881-1890 and 52 in 1891-1900.
An examination of the relative incidence of typhoid in the counties of England and Wales (Bulstrode) goes to show that its prevalence, broadly regarded, is not capricious. The areas of maximum and minimum incidence remained practically the same throughout the twenty years 1871-1890, though there was every where a large diminution. This fact suggests that standing con ditions may be as important as those accidental occurrences which attract public attention by causing sudden and explosive out breaks. When these are on a small scale they may be due to milk; on a large scale they are always water-borne and caused by sud den contamination of a public supply. The classical example is Maidstone. That outbreak began towards the end of August 1897, and within six weeks some 1,500 persons were attacked. The total number of cases was 1,847, with 132 deaths, in a popu lation of about 34,000. With the exception of 28o cases of sec ondary infection, which lingered on till the following January, they all occurred before the i8th of October, and the disease sub sided almost as rapidly as it arose. A mass of evidence of different kinds left no possibility of doubt that accidental contamination of a water-supply was the cause. Perhaps the most striking point is that Maidstone was supplied with water from three different sources, known as Cossington, Boarley and Farleigh, and out of 1,681 cases the respective incidence in these areas was—Cossing ton 29, Boarley 69, Farleigh 1,583. Another great example of water-borne typhoid was furnished by Philadelphia where 14,082 cases occurred in 1898-1899.
Improved knowledge of the nature and causa tion of typhoid fever has not led to the successful introduction of a specific treatment ; nor have means been found to cut short the illness, though its fatality has been reduced. It still goes through the classical stages, which broadly coincide with first, second and third weeks. Attempts have been made to deal directly with the toxins produced by the bacilli, on the hypothesis that they are formed in the intestinal canal, by the use of internal disinfectants, such as mercury, iodine, carbolic acid, salol, etc., and these agents
are sometimes beneficial; but the treatment remains essentially symptomatic, and follows the principles that were recognized be fore the discovery of the bacillus typhosus. One of the most important improvements is the regular use of sponging or bathing for the reduction of temperature. It has even been developed into a continuous bath, in which the patient is kept in water throughout the illness. Since the development of serum-therapy various anti-typhoid sera have been tried in the treatment of the disease but on the whole with indifferent success.
If house drainage were always perfectly carried out, sewage satisfactorily disposed of, water-supply efficiently pro tected or treated, patients segregated, and the typhoid material excreted by them and typhoid "carriers" effectually annihilated— if, in short, scientific cleanliness were completely attained, the disease would disappear, or be at least excessively rare. In some communities much has been done in the directions indicated; but in many others the lessons of experience are ignored, and even the best practice lags behind theory. The most important difficulty is undoubtedly water-supply. The substitution of public water supplies for shallow wells and small streams liable to pollution is one of the greatest factors in the diminution of typhoid and other water-borne diseases ; but it may give rise to danger on a far larger scale, for a whole community may be poisoned at one blow when such a supply becomes contaminated. Unfortunately, it is extremely difficult to prevent contamination with certainty in a populous country. Theoretically, water may be pure at its source, and may be distributed in that condition. Such is water derived from deep wells and springs, or gathered from uncultivated and uninhabited uplands. In the one case it has undergone natural filtration in the ground; in the other, it escapes all risk of pollu tion. These waters are generally pure, but the condition cannot be relied on. A tramp or a shepherd may pollute the most remote gathering-ground unless it be fenced in ; deep wells may be simi larly fouled by workmen, and sewage may find its way into them from the surface or through fissures. To secure purity, therefore, and prevent liability to outbreaks of typhoid and other intestinal diseases, all gathering-grounds should be fenced in, and water, even from deep wells, should be regularly examined, both chemi cally and bacterioscopically, in order that any change in composi tion may be detected. In the water-supplies of great populations such examination should be made daily. Further, all supplies which are not above suspicion should be filtered through sand or sterilized by boiling. The latter can be carried out by simple means in the case of individual domestic water, and attempts have been made to apply it by means of mechanical apparatus to sup plies on a larger scale. It is not, however, applicable to the water supply of large towns. Sand filtration is at present the best mode of dealing with these supplies. There is no purer water than that which has been properly treated by subsidence and sand filtration, even when it is taken from an impure source. So far as the pre vention of typhoid and other water-borne disease is concerned, it is certainly safer than the unfiltered water which is taken from so-called pure sources. It cannot be a mere coincidence that Lon don, Hamburg, Berlin and other towns using well-filtered but originally impure river water should be generally freer from water borne disease than many large towns drawing their supply from purer sources but neglecting to filter it. The table below, pre pared by Mr. Caink, while engineer to the city of Worcester, illus trates this f act, which has also been noted by Professor Saltet of Amsterdam as holding good of the Netherlands.