“During the summer this camp received 20,000 recruits. In October, 1918, the virulent form of influenza struck this camp. It confined itself almost exclusively to the recruits of the summer and scarcely touched the men who had lived through the epidemic of April. Not only the 2,000 who had the disease in April, but the 24,000 who apparently were not affected escaped the fall epidemic. It appears from this that the mild form of influenza of April gave a marked degree of immunity against the virulent form in October. There is another observation which points the same way. Looking over the statistics of the fall epidemic in cities in the United States we find that certain cities had a low death rate, while others had a relatively high rate. Among those cities which had a low death rate we will mention Atlanta, Ga.; Kansas City, Mo.; Detroit, Mich., and Columbus, Ohio. Going to the spring records of these cities we find that in all of them in March and April of 1918 there was an unusually high death rate from pneumonia and undoubtedly in these cities at that time there was a relatively mild epidemic of influenza. In this way I am inclined to account for the relatively low death rate in these cities in the fall of 1918. I make no claim that this and other instances of a similar kind prove that the mild and virulent forms of influenza are manifestations of the same disease, but I do hold that the evidence points that way.” Lemierre and Raymond report the following observation in favor of the development of a certain degree of immunity in the French troops in April, 1918. After an intervening period of quiescence there was a manifest recrudescence at the end of August. Many military formations were attacked during both periods. This was true especially in three groups of an artillery regiment under their observation. In the first of these groups there were three cases in April, while 114 men were attacked in August. In the third group there were 100 cases in April and only 3 in August. In the second group there were 20 cases in April and 59 in August. Their report does not state the total number of individuals in each of the three groups. Joltrain and Baufle discuss the flaring up of the epidemic in October, and relate that a troop of soldiers from Indo-China nearly all had the disease lightly in the spring, but when the disease appeared again it spared this troop completely, while troops and civilians around developed it in a severe form. Gibbon writes: “During the last three waves of the epidemic I had to deal with the sick of 2,000 troops, and during this time we treated in hospital over 400 cases. No cases admitted in June, July or August were re-admitted in October, November, or December, and no cases admitted in either of these two periods were re-admitted in February this year. Unfortunately I am unable to trace the cases into March as the troops were changed.”