CIRCULATION. L07 



lowing method, among others, has been employed : A tube open at both ends 

 is introduced through the external jugular vein of an animal into the right 

 ventricle, or, with greater difficulty, through the carotid artery into the left 

 ventricle. In neither case is the valve, whether tricuspid or aortic, rendered 

 incompetent during this proceeding, nor need the general mechanism of the 

 heart and vessels be gravely disturbed. If the outer end of the tube be 

 connected with a recording mercurial manometer, a tracing of the pressure 

 within the right or left ventricle may be written upon the kymograph. It 

 is found, however, that the pressure within the heart varies so much and so 

 rapidly that the inert mercurial column will not follow the fluctuations, and 

 that the attempt to learu the mean pressure by this method fails. A valve, 

 however, may be intercalated in the tube between the ventricle and the man- 

 ometer — a valve so made as to admit fluid freely to the manometer, but to let 

 none out. The manometer will then record, and record not too incorrectly, the 

 maximum pressure within the right or left ventricle during the experiment; in 

 other words, it will record the greatest force exerted during that time by the ven- 

 tricle in order to do its work. 1 In this way the maximum pressure within 

 the left ventricle of the dog has been found to present such values as 170 and 

 234 millimeters of mercury, the corresponding maximum pressure in the aorta 

 being 158 and 21 2 millimeters respectively. 2 The maximum pressures obtained 

 from simultaneous observations upon the right and left ventricle of a dog are 

 variously reported. It would perhaps be not far wrong to say that in this 

 animal the pressure in the right ventricle is to that in the left as 1 to 2.6. 3 



The work done by each ventricle during its systole is found by multiplying 

 the weight of the pulse-volume ejected into the force put forth in ejecting it. 

 That force is equal to the pressure under which the pulse volume is expelled. 

 If we use as a basis of calculation the pressures observed in the dog's heart with 

 the maximum manometer, we may assume as the measure of a given pressure 

 within the contracting human left ventricle 200 millimeters of mercury, and for 

 the human right ventricle 77 millimeters. If for each column of mercury there 

 be substituted the corresponding column of blood, the heights will be 2.5fi7 

 meters and 0.988 meter respectively. The force exerted by the right or left 

 ventricle upon the pulse-volume might therefore just equal that put forth in 

 lifting it to a height of 0.988 or 2.507 meters. If we assume 100 grams as 

 the weight of a possible pulse-volume ejected by a human ventricle, the work 

 done at each systole of the left ventricle would be 1<»<> 2.567 25<i.7 gram- 

 meters, and at each systole of the right ventricle 100 0.988 98.8 gram- 

 meters; a grammeter being the work done in raising one gram to the height 

 of one meter. The work of both ventricles together would be 256.7 H 98.8 

 = 355.5 grammeters. The foregoing estimates are offered not :is statements 

 of what does occur, but as very rough indications of whal may occur. Even 



1 F. Goltz iind J. Gaule: " Ueber die Druckverhaltnisse im [nnera ties Herzens," Archiv 



J'iir die (/esammtr Phyxiolni/ii', 187N, xvii. S. 100. 



2 S. de Jager : " Ueber die Saugknilt dea Herzens," Pfluger'a Archiv fur du gesammte Physic 

 ologie, 1883, S. 504, 505. < ; "li/. '"><' ( *aule, op. tit., S. 106. 



