Action of Carbon Dioxide and Adrenalin on the Heart. 385 



heart working against a high arterial resistance, may dilate even in the 

 presence of adrenalin. 



Combining the administration of C0 2 and adrenalin in proper proportions 

 may keep the mean heart volume constant, usually in a position shifted to 

 the diastolic side ; and the increased excursions of the lever (fig. 5) correspond 

 with the increased output per beat and output per minute described above. 



I. II. III. IV. 



Fig. 5. — Cardiac Volume and Blood Pressure, showing effect of combining C0 3 and 

 Adrenalin. (I) Normal ; (II) adrenalin : (III) C0 2 and adrenalin ; (IV) CO, off. 

 recovery. Read from left to right. Intervals 2 mins. Systole downvrards ; increase 

 of heart volume caused rise of lever. 



Form of the Heart Volume Curves. — These curves were obtained by means 

 of a glass plethysmograph on the ventricles, the movements being carried by 

 air transmission to the brass piston recorder with vulcanite piston made by 

 Albrecht. The movements of the piston were arranged to write in a vertical 

 plane and recorded on smoked paper (fig. 6). 



Normally, the form obtained by this method consists of a rounded curve, 

 reaching its minimum usually with two points at which the curve changes to 



VOL. LXXXVIII. — B. 2 G 



