Disease, especially when chronic, rarely produces a single or simple change in structure or in function. Physiologic measurements of various sorts that reveal deviation from the normal when applied to patients must therefore be interpreted with caution, for it is not always easy to decide which of the mechanical or chemical changes present is responsible for the abnormal finding. From time to time, however, disease performs a simple experiment, producing a few recognizable alterations in, for example, the dynamics of the circulation: when this occurs, opportunities for study may arise that are not easily created by deliberate intention. Such an opportunity was offered by the following case. Case 1. —History. —A printer, 36 years old, white, entered Vanderbilt University Hospital through the outpatient department on Feb. 16, 1930, with the complaints of shortness of breath and generalized swelling of the body. Previous to the onset of the present illness, the