Dr. S. R. Haythorn, director of the Singer Memorial Laboratory, early in the epidemic became interested in the protection of individuals against the infection. In certain quarters much was claimed for the immunity which could be conferred by vaccination, either by the inoculation of pure B. influenzæ vaccines or by mixed vaccines. Hoping for some results by the use of such vaccines, Dr. Haythorn undertook the preparation of these materials. The value of this procedure could only be estimated after the lapse of some time and at a period when the epidemic was again waning. The clinical work at Mercy Hospital was carried on under the direction of Dr. J. A. Lichty, and assisted by Dr. W. W. G. Maclachlan, Dr. P. I. Zeedick, Dr. F. Klein and Dr. W. J. Fetter. By the close co-operation of the members of this group it was possible to put the clinical findings of one or other member to severe test, so that the recorded observations and deductions are of the greater value and less flavored by the personal element. This is of the more value, since, with the great amount of work which had to be done at the time of the height of the epidemic, it was often not possible for the same individual to bestow the amount of time upon each and all cases as he desired. We are much indebted to Dr. Ogden M. Edwards, dean of the School of Medicine, for making available the facilities for carrying out the work, and for encouraging the publication of the reports. OSKAR KLOTZ. _Pittsburgh_, June, 1919. HISTORY AND EPIDEMIOLOGY OF INFLUENZA By JAMES I. JOHNSTON, M. D.