180 CIRCULATION. 



The cavities of the ventricles are triangular or conoidal 

 the right being broader and shorter than the left, which ex- 

 tends to the apex. The inner surface of both cavities is 

 marked by peculiar ridges and papillae, which are called the 

 columnar carneoe. Some of these are mere fleshy ridges pro- 

 jecting 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 tendinece, which are at- 

 tached 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 evidently facilitates the complete emptying 

 of the ventricles during their contraction. 



The walls of the left ventricle are uniformly much thicker 

 than the right. Bouillaud found the average thickness of 

 the right ventricle at the base to be 2J lines, and the thick- 

 ness of the left ventricle at the corresponding part 7 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 phenom- 

 ena which accompany the heart's action. The direction of 

 the fibres cannot be well made out unless the heart has been 

 boiled for a number of hours, when part of the intermus- 

 cular tissue is dissolved out, and the fibres can be easily sep- 

 arated and followed. Without going into a minute descrip- 

 tion of their direction, it is sufficient to state, in this con- 

 nection, that they present two principal layers: a super- 

 ficial layer common 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 columnse carneae. These fibres envelop 

 both ventricles. They may be said to arise from cartilaginous 

 rings which surround the auriculo-ventricular orifices. The 

 external surface of the heart is marked by a little groove 

 which indicates the division between the two ventricles. 



