ficiently elevated to melt the snow that up to this time had been frozen hard, and during the early days of April there were frequent warm showers. In consequence of these atmospheric conditions the entire mass of dejecta that had been passed by the patient during the course of his illness was washed directly into the stream supplying the reservoirs from which the town obtained the largest part of its water. The amount of pollution was therefore exceptionally great, and the disease-producing elements must have been disseminated by means of the water very shortly afterward; at all events, the evidence that was obtained shows that the first cases of the epidemic appeared within from two to three weeks-the period of incubation of typhoid fever-after the polluted water had been distributed through the town. The accompanying is a chart of Plymouth, with sources of its water, and the distribution of the polluted supply marked .. in red (page 85). The Outbreak in Philadelphia During the Winter of 1897-98.-The city of Philadelphia receives its water-supply in large part direct from the Schuylkill river, a more or less grossly-polluted stream that traverses a thickly-populated section of Pennsylvania, and finally unites with the Delaware river to the south of the city. During December, 1897, January, and a part of February, 1898, the weekly returns of the Health Officer of the city revealed the fact that typhoid fever had suddenly appeared in Philadelphia to such an extent as to be fairly regarded as epidemic; the number of cases reported between November 27, 1897, and March 1, 1898, having been 1927 as compared with 628 cases for the same period of 1896-97 and as against a weekly average of 40 cases for the eight weeks preceding December, 1897. In short, during the period of greatest prevalence the number of cases reported weekly was somewhat over three times as great as under usual conditions. Upon locating these cases the increase was found to be general throughout the city, but the majority of the cases (about 65 per cent.) occurred within a sharply-circumscribed area in the northern section of the city that embraces princi pally the 15th, 20th, 28th, 29th, 32nd, 27th, and 38th wards (see shaded area on Map, page 89), having a population roughly representing only about one-fifth of the entire population (census 1890). As soon as this state of affairs became evident a careful inspection, including chemical and bacteriological analysis of the milk and water-supplies of this section especially, was ordered by the Board of Health. The results of careful studies upon the problem by laboratory methods shed no important light upon the origin and mode of dissemination of the disease. It was clear to those engaged upon the investigation' that the cause of the outbreak must have been operative at some period antecedent to the epidemic outbreak of the disease; that infection of a large number of persons must have occurred simultaneously and probably through the same channel; and that, taking four to six days as the time necessary to recognize the disease and notify the Board of Health, and seven to ten days as the period of incubation of typhoid fever, infection must have occurred during the week ending November 20, 1897. On referring to the events of this week it was found that on the afternoon of November 16 there was suddenly deposited into the Schuylkill river, as a result of the overflow of the large intercepting sewer carrying the sewage of a great portion of northern Philadelphia, a large volume of raw sewage. The point at which this occurred was located on the same side of the river and but a short distance up stream (a few hundred feet) from the intake of the pumping station that supplies water to the Queen Lane Reservoir. At the time of the accident and for about two hours afterward, the pumps were engaged in filling this reservoir, and a very large. portion of the grossly-polluted water must have been pumped directly into it. The pumps at the stations located further down the stream were stopped a few hours after the accident "because the water was discovered to have a peculiarly bad 1 In this connection I wish to say that the success of this investigation was in large part due to the valuable services rendered by Dr. H. D. Pease, at the time First Assistant in the Laboratory of the Board of Health of Philadelphia. Black bars, for the entire city; red bars, for wards in Queen Lane CHART 14-Showing incidence of typhoid fever in Philadelphia. taste," so that all the reservoirs below the point of pollution were more or less contaminated, though that at Queen Lane, because of the proximity of its intake, was, as subsequent events demonstrated, most affected. Upon inquiry as to the distribution of the water from the Queen Lane Reservoir, it was ascertained, through the courtesy of Mr. J. C. Trautwine, Jr., Chief of the Bureau of Water, that the area supplied with water from this reservoir was embraced within the limits of the wards in which the largest proportion of cases of typhoid fever occurred. The connection, therefore, between the typhoid cases in these wards and the character of water supplied to them was, in the judgment of those engaged in the investigation, reasonably established; even though repeated bacteriological examination of the water had failed to demonstrate the presence of typhoid bacilli in it. It is not necessary to discuss here the increase of typhoid fever in other sections of the city; it suffices to say that circumstantial evidence connects it also with the polluted watersupply. By reference to Chart 10 the progressive incidence of the cases, and the relation between those in the most affected district and those in the city generally, will be seen. graphically represented.1 Chart 14 shows the typhoid morbidity in Philadelphia in the winter of 1897-98. The period represented embraces two months prior to the discharge of raw sewage into the river, and three months after the epidemic had reached its maximum. (Compiled from official reports of the Health Officer.) Black bars represent the number of cases weekly for the entire city. Red bars represent the number of cases occurring at the same time in the district supplied by the Queen Lane Reservoir into which the greatest amount of sewage was pumped. The population of this district was about one-fifth of the entire city. To emphasize further the important relation between the 1 For details, see Annual Report of the Department of Public Safety of Philadelphia, 1898; section referring to the Division of Bacteriology, etc., of the Bureau of Health. |