ANATOMY OF THE HEART. 



37 



16 v 



16 



is from 143 to 212 cubic centimeters, or from about 4-8 to 7 ounces. This is much 



greater than most estimates, which place the capacity of the various cavities, moderately 



distended, at about 2 ounces. 



Notwithstanding the disparity in the 



extreme capacity of the various cavities, 



the quantity of blood which enters these 



cavities is necessarily equal to that which 



is expelled. This has been stated to be 



a little more than two ounces. There 



are no means of estimating with exact- 

 ness the quantity of blood discharged 



with each ventricular contraction ; and 



we find the question rather avoided in 



works on physiology. All we can say 



is that, from observations on the heart 



during its action, it never seems to con- 

 tain much more than half the quantity in 



all its cavities that it does when fully 



distended by injection ; but it is the right 



cavities which are most dilatable, and 



probably the ordinary quantity of blood 



in the left ventricle is from four-fifths to 



five-sixths of its extreme capacity. 



The cavities of the ventricles are 



triangular or conoidal, the right being 



broader and shorter than the left, which 



extends to the apex. The inner surface 

 of both cavities is marked by peculiar 

 ridges and papillae, which are called 

 columnae earner. Some of these are 

 mere fleshy ridges projecting into the 

 cavity; others are columns attached by 

 each extremity and free at the central 

 portion; and others are papilla) giving 

 origin to the chordae tendineae, which are 

 attached to the free edges of the auriculo- 

 ventricular valves. These fleshy columns 

 interlace in every direction and give the inner surface of the cavities a reticulated ap- 

 pearance. This arrangement evidently facilitates the complete emptying of the ventri- 

 cles during their contraction. 



The walls of the left ventricle are uniformly much thicker than on the right side. 

 Bouillaud found the average thickness of the right ventricle at the base to be two and 

 a half lines, and the thickness of the left ventricle at the corresponding part, seven lines. 

 The arrangement of the muscular fibres constituting the walls of the ventricles is 

 more regular than in the auricles, and their course enables us to explain some of the phe- 

 nomena which accompany the heart's action. The direction of the fibres cannot be 

 well made out unless the heart have been boiled for a number of hours, when part 

 of the intermuscular tissue is dissolved out, and the fibres can be easily separated and 

 followed. Without going into a minute description of their direction, it is sufficient to 

 state, in this connection, that they present two principal layers ; a superficial layer com- 

 mon to both ventricles, and a deep layer proper to each. The superficial fibres pass 

 obliquely from right to left from the base to the apex ; here they take a spiral course, 

 become deep, and pass into the interior of the organ to form the columnar carneaa. 



FIG. 13. Left cavities of the heart, (Bonamy and Beau.) 

 1, left ventricular cavity ; 2, mitral valve; 8, 4, columnar, 

 carnece; 5, aortic opening; 6, aorta; 7, 8, 9, aortic 

 valves; 10, right ventricular cavity; 11, interventricular 

 septum ; 12, pulmonary artery ; 13, 14, pulmonic valves ; 

 15, left auricular cavity; 16, 16, right pulmonary veins, 

 with 17, 17. openings of the veins ; 18, section of the cor- 

 onary vein. 



