1. An epidemic of diarrhoea or gastro-enteritis occurring in Aberdeen in 1919, and causing over 1000 cases and 72 deaths, has been proved to be due to infection of milk with dysentery bacilli of the Flexner type.

2. Similar epidemics of milk-borne diarrhoea have occurred formerly, but bacteriological investigation had failed to determine the nature of the infecting organism. Keference to the epidemiological and clinical features of such former epidemics, however, makes it practically certain that they were essentially of the same description as the Aberdeen epidemic of 1919, and accordingly indicates that they were likewise due to infection of milk with dysentery group bacilli.

3. The Aberdeen epidemic of milk-borne bacillary dysentery had run its course and had caused 72 deaths before serological proof of bacillary dysentery was available. Since the time of the Aberdeen investigation, notable advances have been made in methods for the bacteriological diagnosis of the dysenteries as a result of the fundamental work of F. W. Andrewes, A. D. Gardner, C. J. Martin and others. Nevertheless, modern methods of bacteriological diagnosis are not infallible, and the Aberdeen experience clearly indicates that deaths will be prevented if polyvalent anti-dysenteric serum and saline treatment are used at once in a disease having the clinical symptoms of bacillary dysentery, or in an acute enteritis from which has been isolated organisms with the cultural reactions of the dysentery group bacilli.