PHYSIOLOGICAL ANATOMY OF THE HEART. 



35 



10 



and probably the ordinary quantity of blood in the left ventricle is four- 

 fifths to five-sixths of its extreme capacity, or five to six ounces (120 to 

 170 c.c.). 



The cavities of the ventricles are triangular or conoidal, the right being 

 broader and shorter than the left, which latter extends to the apex. The 

 inner surface of both cavities is marked by ridges and papillae, which 

 are called columnae carneae. Some of these are fleshy ridges projecting 

 into the cavity ; others are columns attached by each extremity and free at 

 the central portion; and others are papillae 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 appearance. This arrangement facilitates 

 the complete emptying of the ventricles during their contraction. 



The walls of the left ventricle are uniformly much thicker than those of 

 the right side. The average thick- 

 ness of the right ventricle at the 

 base is two and a half lines (5*25 

 mm.), and the thickness of the 

 left ventricle at the corresponding 

 part is seven lines (14'7 mm.), or 

 a little more than half an inch 

 (Bouillaud). 



The arrangement of the mus- 

 cular fibres constituting the walls 

 of the ventricles is more regular 

 than in the auricles, and their 

 course affords an explanation of 

 some of the phenomena which 

 accompany the heart's action. 

 The direction of the fibres can 

 not be well made out unless the 

 heart have been boiled for a num- 

 ber of hours, when part of the 

 intermuscular tissue is dissolved 

 out, and the fibres can be easily 

 separated and followed. Without 

 entering into a minute descrip- 

 tion of their direction, it is suffi- 

 cient 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 ventri- 

 cle. 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 



FIG. 15. Right cavities of the heart (Bonamy and Beau). 



1, right ventricular cavity ; 2, posterior curtain of the 

 tricuspid valve ; 3. right auricular cavity ; 4, colum- 

 nar carnece of the right auricle ; 5, section of the cor- 

 onary vein ; 6, Eustachian valve ; 7, ring of Vieus- 

 sens ; 8, fossa ovalis ; 9. superior vena cava ; 10, infe- 

 rior vena cava \ 11, aorta ; 12, 12, right pulmonary 

 veins. 



