_Mortality curves._—Pearl has studied the epidemic constitution of influenza in forty-two of the large cities of the United States. He has plotted the annual death rate per 1,000 population from all causes in each week, from the week ended July 6, 1918, up to January 1, 1919, and observed a very distinct difference in the type of curve for deaths from all causes during the epidemic period in the various cities. These differences have been chiefly in respect to the severity and suddenness with which they were attacked. Thus Albany, Boston, Baltimore, Dayton and Philadelphia show an initial explosive outbreak of great force, while Atlanta, Indianapolis, Grand Rapids, Milwaukee and Minneapolis exhibit a much slower and milder increase of the mortality rate. In Albany and Baltimore the curve of the first epidemic outbreak rises to a peak and declines at about the same rate. In Cleveland and St. Paul, on the other hand, the rate of ascent to the peak is very rapid, while the decline is slow and long drawn out. Some of the cities, such as Albany, show but a single well defined peak in the mortality curve. Others, such as Boston, New Orleans and San Francisco show two peaks; while still others, like Louisville, show three well marked peaks. Usually the first was the highest and the second and third were progressively lower. Milwaukee and St. Louis, on the other hand, showed second peaks higher than the first. The usual phenomenon, however, was a large first wave followed by smaller ones. The highest, or maximum peak rate of mortality during the epidemic varied greatly, from 31.6 per 1,000 in the case of Grand Rapids, to 158.3 per 1,000 in the case of Philadelphia. The death rates which were of the most frequent occurrence were, generally speaking, rates below 70 per 1,000 per week. The date of the week in which the maximum peak rate occurred was earliest in Boston and Cambridge, where it occurred October 5th, and latest in Grand Rapids, Milwaukee and St. Louis (December 14th). Thirty-one of the 40 cities studied had attained the peak rate of mortality prior to November 2d. In the case of Milwaukee and St. Louis the maximum peak was the second peak, whereas in Grand Rapids it was the first peak that was so late. Sixty-five per cent. of the 40 cities showed two distinct peaks in the mortality curve, while 15 per cent. had one peak, and 8 or 20 per cent. had three peaks.