I shall describe in this paper a simple, practical clinical test which is useful in the diagnosis of anemia and plethora, and which is accurate and dependable in the hands of those who are well acquainted with it. In fact, I believe, it is one of the most accurate and dependable methods of detecting slight grades of anemia or plethora. Through its use, one can detect a gain or loss of 200 cc. of blood given by transfusion or withdrawn by venous section.
In the earlier days of medical science, a diagnosis of anemia or plethora depended on examination of a patient's color, or the color of a freshly drawn specimen of blood. In more recent years, laboratory estimations of the red count and percentage of hemoglobin have gained precedence over this simple practical method of examination. Since the introduction of methods of estimating plasma volume and blood volume, there