demic.-Conspicuous among them may be mentioned the oft-cited outbreak of typhoid fever in Lausen in Switzerland. This village, prior to the outbreak to which reference is made, had never been visited by an epidemic of typhoid fever, and for years there had not been known a single sporadic case of the disease. In 1872 typhoid fever appeared in the village, and before its disappearance about 17 per cent. of the inhabitants had been attacked. On Lausen is situated in the province of Basle just north of the mountain ridge Stockhalden (Fig. 2), which separates it from the Fürlerthal. In a solitary farm-house in this valley lived a peasant, who was attacked with typhoid fever on June 10, after having been away on a visit. Between June 10 and August a girl and the farmer's wife and son, all inmates of the same house, were attacked with the same disease. August 7 the disease appeared in Lausen and almost simultaneously 10 individuals were stricken down; during the next ten days 57 persons were affected; by the end of the fourth week the epidemic numbered 100 cases, and at its close in October 130 of the 780 residents of the town had suffered from the disease. In addition to this, 14 children, who had been spending their holidays in the town, developed the disease after their return to school. The cases were pretty evenly distributed throughout the village, with the exception of six houses. These six houses had their own private wells from which their domestic watersupply was drawn. This fact directed suspicion to the source from which the town drew its water-supply. This supply came from a spring at the foot of the north side of the Stockhalden ridge which separated Lausen from the farm-house to which reference has been made. Observations upon a brook in the Fürlerthal, near which the peasant lived, and of the water-supply of Lausen gave rise to the suspicion-ultimately proved to be correct-that there might be a direct communication between the two. It had been noted that, ten years previously, a hole had spontaneously formed in the soil, a little below the farm-house, and that whenever the meadows below this hole were inundated by water from the Fürler the volume of the spring supplying Lausen became rapidly augmented. The Fürler was in direct communication with the closets and dung-heaps of the affected house. The intestinal evacuations from the inmates were thrown into it, and their soiled clothing was washed in it, and it was with the waters of this brook that the meadows had been inundated from the middle to the end of July. The epidemic began at Lausen about three weeks after this inundation. To fix further the connection between the polluted water of the Fürler and the spring at Lausen, Dr. Hägler, who investigated the case, made an experiment which demonstrated that the epidemic in Lausen was the outcome of the use of water polluted by the dejecta from the patients in the Fürlerthal, on the other side of the mountain ridge. The hole near the farm-house in the Fürlerthal was opened, and the brook led into it; after three hours the volume of water given out by the spring at Lausen was doubled; about 18 hundred-weight of common salt was now poured into the hole, and in a very short time the water at Lausen gave the characteristic chemical reaction of this salt, the amount of which gradually increased until analysis showed the amount of salt present to be about threefold of what it was at the beginning. The experiment cleared away all doubt as to the means by which the disease reached Lausen, and the channel through which it was disseminated. The Wittemburg Epidemic.-Still another example of the dissemination of typhoid fever through drinking water, which is of interest not only for this alone, but is especially instructive as an illustration that this disease can arise only from the use of waters that are contaminated with the specific causative agent of typhoid fever, and that the use of water not so contaminated, but equally foul in so far as other pollutions are concerned, does not result in the appearance of this disease. The case in point is recorded by Gaffky and is as follows: In June, 1882, there appeared among the privates of the 1 Gaffky: Mittheilungen aus dem Kais. Gesundheitsamte, 1884, Bd. ii., S. 410. 3rd Brandenburg Infantry regiment located at Wittemburg, an epidemic of typhoid fever which, by virtue of its sudden appearance and dissemination (Chart 13) and its limitation to one battalion of this regiment, offered a favorable prospect for the discovery of the causes underlying its existence. The three companies of this battalion, in which the disease broke out, numbered 386 men, 226 of whom were quartered in the arsenal, while the remaining 160 were quartered in private houses in the town. Of the 160 men quartered in 17 private houses in the town, 24 suffered from typhoid fever, while not a single case occurred among the other inmates of these houses. Indeed, during the course of the epidemic not a single case was reported among the citizens of the town. From this it seemed probable that the cases of typhoid fever that had occurred among the soldiers quartered both in the barracks and in the town had been infected from the same source. After careful inspection of all other possible channels through which the men could have become infected, the water-supply was finally subjected to investigation. The water used by the troops was supplied by two wells, one situated in the yard of the barracks near a privy, the other just outside the barracks yard in the neighboring Burgomeisterstrasse. Upon chemical analysis and careful inspection, both wells revealed considerable contamination, though because of the more agreeable taste of the water in the well outside the barracks yard, in a neighboring street, this was more commonly used for drinking purposes by both soldiers and citizens than was the water of the well within the barracks yard. Investigation showed that some time prior to the outbreak, typhoid dejecta had been thrown into the barracks privy, which is situated about 50 feet north of the well in the yard, and upon examining the walls of this privy, which were cemented and had hitherto been supposed to be proof against breakage, two cracks of appreciable size were found, through which the contents had leaked. The strata between this privy and the well were for the |