AN ANATOMICAL STUDY ON THE 



so that there is a relation between the ventricular 

 capacity in contraction and in dilatation. Since the 

 ventricles in dilating do not become filled with 

 nothing, or with something imaginary, so in con- 

 tracting they never expel nothing or something 

 imaginary, but always blood in an amount pro- 

 portionate to the contraction. 



So it may be inferred that if the heart in a single 

 beat in man, sheep, or ox, pumps one dram, and 

 there are i,ooo beats in half an hour, the total 

 amount pumped in that time would be ten pounds 

 five ounces; if two drams at a single stroke, then 

 twenty pounds ten ounces; if half an ounce, then 

 forty-one pounds eight ounces; and if one ounce, 

 then a total of eighty-thre e pounds four ounces, all 

 of which would be transferred from the veins to 

 the arteries in half an hour. 



The amount pumped at a single beat, and the 

 factors involved in increasing or diminishing it, 

 may perhaps be more carefully studied later from 

 many observations of mine.^ 



2 This has remained a most important question ever since. An 

 excellent general review of the subject is Y. Henderson's Volume 

 Changes of the Hearty Physiol. Rev., 3: 165, 1923. Various types of 

 experiments indicate a "stroke volume" of the heart of 1.5 to 2 cc. per 

 kilo body weight, maintained with a fair degree of constancy. In 

 the effort to find a simple satisfactory method to measure cardiac out- 

 put, Y. Henderson and H. Haggard (Amer, J. Physiol., 73: 193, 1925) 

 propose the determination of the rate of absorption of a slightly solu- 

 ble gas, suggesting ethyl iodide. The difference between the ethyl 

 iodide content of inspired and expired air times the minute-volume 

 of respiration gives the minute-volume of the gas absorbed. The 

 alveolar concentration times the coefficient of solubility gives the 



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