The Influence of Temperature on the Output of the Heart

While investigating the influence of the viscosity of the blood on the output of the heart, I observed that the cardiac discharge depends in a large measure on the temperature of the fluid used to vary the viscosity. This observation prompted me to disregard secondary effects for the present and to determine, first of all, the relationship between the temperature of the blood and the cardiac output. The output of the heart was ascertained in accordance with the method of Rothberger. 1 The heart was placed in an oncometer of glass, the changes in the volume of the heart being recorded by air transmission. Rothberger confined his measurements to the changes in the ventricles, the volumetric variations of which were obtained by covering the large orifice of the oncometer with a rubber membrane and by inserting the organ up to its auriculoventricular junction through a central opening in the