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W. H. Howell and F. Donaldson. [May 31, 



At the suggestion of Professor Martin, and under his directions, we 

 undertook some experiments upon this subject, making use of his 

 method of isolating the heart. The quantity of blood ejected from the 

 left ventricle at each systole under varying conditions of venous pres- 

 sure, arterial pressure, and pulse-rate, can be determined directly with 

 this method by catching the blood as it is pumped out from the tube 

 connected with the aorta of the dog. 'In all the observations made the 

 blood was collected during^a period of 30 seconds, and the quantity thus 

 obtained divided by the number of heartbeats occurring during that 

 time, as shown on the kymograph, in order to determine the quantity 

 pumped out at each S3^stole. The results of our work fall under four 

 different heads. 



I. The Maximum Quantity of Blood vfkic% can he thrown out from the 

 Left Ventricle at a single Systole. 



The method of working in determining this quantity was to increase 

 the amount of blood flowing into the right side of the heart, by 

 raising the supply flask connected with the .superior vena cava, until 

 a limit was reached in the amount of blood pumped out from the left 

 ventricle, i.e., a point beyond which increase. of the pressure and the 

 quantity of 'the blood flowing into the right. side of the heart caused 

 no increase in -the quantity of the blood sent out from the left 

 ventricle. 



The main result of these experiments may be stated at follows : 

 With a mean pulse-rate of 180 per minute in the dog, the mean, ratio 

 of the maximum weight of blood pumped out from the left ventricle 

 at each systole to the body- weight is or '00117. The maximum 

 outflow from the left heart was obtained in all cases at or 'below a 

 venous pressure on the right side of 60 centims. of defibrinated calf's 

 blood (46 millims. of mercury). 



With regard to -the maximum outflow from the left ventricle at the 

 normal pulse-rate (120 per minute) of a dog, we have only one 

 experiment to offer. According - to that experiment the ratio of the 

 maximum weight of blood pumped out from the left ventricle at each 

 systole to the body-weight, with a pulse-rate of 120 -per minute, is 

 about or '0014. 



In applying these results to the normal dog, we believe that the 

 average quantity of blood pumped out from the left ventricle at 

 each systole in the living dog is approximated most nearly in our 

 experiments by the maximum outflow;: in other words, we think it 

 probable that the left ventricle during life is distended at each 

 diastole to about its maximum capacity. In coming to this conclusion 

 we were influenced chiefly by three considerations. 1. The same 

 opinion has been expressed by Hoyar, the result of his work on the 

 frog's heart. 2. Calculations of the time required for a complete 



