472 C. R. BARDEEN 



round number which expressed with fair accuracy the specific 

 gravity of the heart as a whole. 



The volume of the empty heart in centimeters may therefore 

 be taken as equal to the weight of the heart in grams divided 

 by 1050. The ratio between the volume of the empty heart and 

 that of the heart in diastole can be estimated from cadavers 

 and from experimental work on animals. The chief difficulty 

 lies in the determination of the volume of the heart in diastole. 



In order to determine the ratio between the volume of the 

 empty heart in dogs and the volume of the heart in diastole, I 

 have made a number of experiments in cooperation with Dr. J. 

 A. E. Eyster and other members of the department of physiology 

 at the University of Wisconsin. The dog was weighed and its 

 pulse at rest under morphine was counted before beginning the 

 experiment. The animal was then anaesthetized, the thorax 

 opened and hgatures were placed about each of the vessels en- 

 tering the heart. With the help of several assistants these liga- 

 tures were tightened simultaneously at a given signal so as to 

 close off the vessels during diastole. The heart was now re- 

 moved from the body and its volume estimated. It was emp- 

 tied and the volume of the cardiac tissue was measured and its 

 weight determined. The ratio of the volume of the empty 

 heart to that of the heart in diastole could then be ascertained. 

 In order to make the pulse correspond approximately with the 

 normal pulse as determined before the experiment, or some- 

 what slower, the vagus nerve was stimulated during the experi- 

 ment to the requisite amount. The chief difficulty in the ex- 

 periment is that of tying off all the vessels simultaneously at 

 the height of diastole. 



Table 18 shows the result of six experiments. The percentage 

 of the diastolic heart volume occupied by the blood in the heart 

 chambers varied from 26 to 46 with an average of 40.6. It is 

 probable that the smaller percentage represents a heart in which 

 we did not succeed in tying bff all the vessels in diastole. If we 

 omit this heart the average becomes 43.5. The average empty 

 heart volume in these dogs was therefore 59.4 per cent if ex- 

 periment 5 is included, 56.5 per cent if this experiment is not 



