1870.] 



four Orifices of the Heart. 



275 



fibres pass from the left to the right ventricle and dip in or bend at the 

 track of the anterior coronary artery to become continuous with fibres 

 having a similar direction in the septum"*. 



2. In the next place, it must be admitted that equal volumes of blood 

 pass in exactly equal and the same times through any two corresponding 

 orifices of the heart ; for if, for example, we could suppose the quantity 

 thrown out through the pulmonic orifice into the lungs to be persistently 

 greater than the amount thrown out in the same time through the aortic 

 opening into the general circulation, it would inevitably follow that over- 

 whelming pulmonary engorgement, cessation of flow from the right heart, 

 and death would rapidly ensue. The alternative supposition of the right 

 ventricle persistently discharging into the lung-capillaries an amount of 

 blood actually less than the quantity as persistently set forth by the left 

 ventricle into the systemic circulation, involves a physical contradiction un- 

 necessary to refute. Whatever, therefore, may be the actual capacities of 

 the ventricles, or the quantities which under pressure they maybe made to 

 contain, this law must be always paramount to enable the healthy heart to 

 act freely and without the production of a congested or overloaded condition 

 of the pulmonic or systemic circulations ; the quantities of blood entering 

 the ventricles synchronously must be equal, and the quantities leaving them 

 synchronously must also be equal ; and to prevent the occurrence or pro- 

 duction of cardiac congestion the quantity of blood received by the ventricles 

 in diastole must equal the quantity expelled by the ventricles in systole, 

 small deviations being allowed within certain limits of health. We shall see 

 the bearing of these latter remarks when we consider the mode in which 

 hearts much diseased in their orifices and valvular apparatus are often 

 enabled to carry on a tolerably unembarrassed circulation, and with but 

 little functional disturbance experienced by the individual so circumstanced. 



The anatomy of the organ fully corroborates the principle we are seeking 

 to establish ; for we are told that " the capacities of the ventricles are pro- 

 bably equal " (Cruveilhier) ; and again, " there are reasons for believing 

 that during life any difference between the capacities of the ventricles is 

 very trifling, if it exist at all"f. 



And lastly, " the whole, or very nearly the whole of the blood contained 

 in the ventricles is discharged from them at each systole ; for the left ven- 

 tricle is frequently found quite empty after death ; and if a transverse 

 section be made through the heart in a state of well-marked rigor mortis 

 (which may be considered as representing its ordinary state of complete 

 contraction), the ventricular cavity i3 found to be completely obliterated." 



From these considerations we may, I believe, fairly assume that 



✓ j x f Equal times of ventricular contraction, 

 I Equal times of ventricular dilatation, 



* Phil. Trans, part 3, 1864. 



t Quain's ' Anatomy,' by Dr. Sharpey, vol. iii. p, 255. 



Y 2 



