PHYSIOLOGICAL ANATOMY OF THE HEART 



37 





The arrangement of the muscular fibres of the ventricles is more 

 regular than in the auricles ; but their direction cannot be well made 

 out unless the heart has been boiled for a number of hours, when part 

 of the intermuscular tissue is dissolved. They present two principal 

 layers, a superficial layer common to both ventricles, and a deep layer 

 proper to each ventricle. The superficial fibres pass obliquely from right 

 to left from the base above to the apex below; here they take a spiral 

 course, become deep and pass 

 into the interior to form the 

 columnae carneae. These fibres 

 envelop both ventricles. They 

 may be said to arise from car- 

 tilaginous rings that surround 

 the auriculo-ventricular ori- 

 fices. The external surface 

 of the heart is marked by a 

 groove that indicates the divi- 

 sion between the two ventri- 

 cles. The deep fibres are 

 circular, or transverse, and 

 surround each ventricle sepa- 

 rately. 



The muscular tissue of the 

 heart is of a deep red color 

 and resembles, in its gross 

 characters, the tissue of ordi- 

 nary voluntary muscles ; but 

 as already intimated, it pre- 

 sents certain peculiarities in 

 its minute anatomy. The 



fibres are Considerably Smaller . J- superficial fibres common to both ventricles ; 2> fibres 



f of the left ventricle ; 3, deep fibres passing upward toward 



and are more granular than the base of the heart; 4, fibres penetrating the left ven- 



those of ordinary muscles. 



They are, moreover, connected with each other by short inosculating 

 branches and have no sarcolemma. The muscular-fibre cells have 

 each a single oval nucleus which presents a network of chromatin. 

 Sometimes, though rarely, a cell contains two nuclei. The cells are 

 joined together by their ends with what seems to be a cement-sub- 

 stance, with delicate protoplasmic processes extending between two con- 

 tiguous cells. The branching fibres form a close muscular reticulum in 

 the meshes of which are bloodvessels, nerves and a small quantity of 

 areolar tissue. This arrangement favors the complete expulsion of the 



Fig. 21. Muscular fibres of the ventricles (Bonamy 

 and Beau). 



