EPIDEMIC PREVALENCE IN THE LIGHT OF EXPERI- MENTAL FINDINGS

This is perhaps a timely occasion to classify and evaluate the results of seven years ' experimental study of epidemic diseases. At the annual meetings of this association in 1921, Flexner (1) outlined a plan for the investigation of mouse typhoid infection under the con-trolled conditions of the laboratory; previously, Topley (2), in London, delivered the Goulstonian lectures on the same subject. Since then, the English investigators, the group at the Rockefeller Institute in New York, and Neufeld and Lange, in Germany, have furthered these studies and brought them to a state suitable for discussion. Hence,. although admirable critiques have already been published recently by Neufeld (3), Topley (4), and Flexner (5), it may be of use to summarize briefly our own conclusions, and relate them as far as possible to epidemic prevalence in man. Furthermore, there is special need at present for a restatement of the general problem, a classification of current theories, and formation of a basis for further investigation. This implies a review of methods and techniques employed, with a discussion of the mutual relation-ship, advantages, and limitations of each. To these questions, there-fore, it is proposed to give attention as well as to summarize briefly the actual results obtained. The first step in the experimental study of an epidemic disease is the close observation of the infection as it occurs naturally. Knowl-edge of the distribution of the specific microbes in nature, their portal of entry into the animal body, various types of animal response, etc., is essential. Thus prepared, one is in a position to plan experiments under conditions which are controlled and yet simulate nature, and to attain results which are relatively free of a certain inevitable labora