Unfortunately, prior to the year 1869, no distinction between typhus and enteric fevers was made in the RegistrarGeneral's returns of births and deaths in Dublin, but we have analysed the returns for four years, in which such a distinction was made, and the results may be looked upon as at all events approximate to the truth. In the first place, during the nine years, 1864–1872, fever in general proved most fatal in the third and fourth weeks of the year (with 10.1 and 9.7 deaths on the average respectively), and least fatal in the twenty-eighth and twenty-ninth weeks (with 44 and 4.3 deaths on the average respectively), that is, the disease was most severe about the period of greatest cold, and least so early in July. In the following Tables, in which the year has been divided into thirteen periods of four weeks each, corresponding results are brought out. In Table XXIX. are grouped the mean number of deaths from fever, as well as those of the other endemic diseases we have been considering, into thirteen periods. From this Table, it will be seen that fever becomes very fatal in autumn, when the mean temperature falls below 54°, the mortality continues to rise with the falling temperature until January and February are past. Early in March the mortality declines, but rises again at the beginning of May, coincidently, it would seem, with a lower humidity. The decline is then very rapid, and the minimum is reached in the seventh and eighth periods-that is, in July and the first half of August. It is worthy of note that the sudden fall in the number of deaths in the seventh period follows the rise of mean temperature above 54° at an interval of some three or four weeks. Temperatures higher than 54° would, therefore, seem to have a controlling influence on the prevalence of fever, while temperatures below 54° seem to favour its development. TABLE XXIX.1-Showing the Mean Number of Deaths in Dublin from (1) Measles, (2) Whooping-cough, (3) Scarlatina, and (4) Fever; and the Mean Temperature, in 13 periods of 4 Weeks, during the years 1864–72 : 1 With respect to this and the following Table, it is necessary to explain that the fall in death-rate noticed in the thirteenth period, or last four weeks of the year, is apparently due to delay in registration at Christmas time. Table XXX. shows the apparent influence of season on the two principal continued fevers-typhus and enteric. TABLE XXX.-Showing the Mean Number of Deaths from Fever in general, and from Typhus and Enteric Fever, and the Mean Temperature, in 13 Periods of 4 Weeks, during the Years 1869-72: The death-rate from typhus reaches a minimum in the ninth period, while the minimal death-rate from enteric fever has already occurred in the eighth period, this fever exhibiting-as the summer rolls by—a decided tendency to increase at an earlier period than typhus. In this same Table the calculated percentages of the two diseases are also entered, and a striking increase in the percentage amount of enteric is noticed towards the close of the year. The highest percentages of typhus are met with, on the contrary, in the seasons of winter, spring, and early summer. The reason for all this is not far to seek. Typhus is often intimately related to overcrowding, and bronchial or thoracic affections are amongst its most frequent complications. Hence we should expect to meet with it especially in the colder seasons. Enteric fever, on the other hand, is connected with a specific contamination of air or water by sewage matter, and its secondary phenomena are developed generally in connexion with the digestive system. Hence a great prevalence of this disease was to be looked for in the warmer seasons, and more particularly at a time when the first autumn rains had washed into drinking wells, and other sources of water supply, the decomposing matters which had been innocuous so long as the skies were clear and the sun still high in the heavens. |