1030 PHYSIOLOGY 



which writes on a blackened surface. The excursions of this lever are 

 proportional to the diminution in volume of the heart at each systole 

 and therefore serve as a measure of the output of the ventricles. Instead 

 of this brass sphere a glass cardiometer may be used (Henderson) 

 consisting of a glass sphere with a wide opening, with a rubber dia- 

 phragm which is slipped on the heart until the edge of the diaphragm 

 rests in the auriculo- ventricular groove (Fig. 407). 



An attempt has been made to determine the output of the ventricles from 

 the time taken up in the total circulation. A solution of methylene blue injected 

 into the central end of the jugular vein can be detected in the blood flowing 

 from the peripheral end of the same jugular after twenty-seven heart-beats. 

 This has been interpreted erroneously as equivalent to saying that the whole 



FIG. 407. Henderson's glass cardiometer. 



blood made the whole circuit of the vascular system and therefore passed through 

 the heart twice in twenty-seven heart-beats. Thus we should have only to divide 

 the quantity of blood in man (3000 grm. in a man of 60 kilos) by 27 in order 

 to arrive at the output of eacl. Ventricle at each cardiac systole, i.e. about 111 grm. 

 It is evident, however, that 'he figure ojbtained by the methylene -blue method 

 merely represents the shortest possible time in which any given particle of blood, 

 taking all the short cuts which may be open, can travel round the whole circula- 

 tion, so that the true output c f the left ventricle in man must be considerably 

 less than 111 grm. and is prolv jly not more than one-half of this amount. 



Zuntz has employed an indirect method of determining the output of each 

 ventricle based on a comparison of the differences in gases contained between 

 arterial and venous blood and the actual amount of oxygen taken from the air 

 in the lungs. Thus in one case he found that in a horse weighing 360 kilos 2733 c.c. 

 of oxygen were taken up in the lungs per minute, while the arterial blood contained 

 10-33 per cent, more oxygen than the venous blood. Since therefore every 

 100 c.c. of blood that passed through the lungs had taken up 10'33 c.c. of oxygen, 

 and 2733 c.c. had been taken up in the course of a minute, it is evident that 



100 x 2733 



-loir- - 26 > 457c - c - 



of blood must have passed through the lungs in the time. This therefore was 

 the output of blood by the right ventricle in a minute and was equivalent to 

 00122 of the body-weight per second. 



