591 CIRCULATORY APPARATUS. 



axis of the ventricles. It is from the apposition of the right and left systems 

 that the ventricular septum is formed. 



b. Unitive fibres of the ventricles. — These are disposed as an external shell 

 enveloping the proper fibres. They leave the fibrous zones at the base of the 

 heart, and descend towards its apex : those of the right side, by inclining 

 forward ; the anterior, in following the direction of the great axis of the 

 ventricles ; those of the left face, by directing their course downwards and 

 backwards ; and the posterior, in roUing themselves from left to right around 

 the left ventricle. On arriving near the point of the heart, they turn from left 

 to right, and before to behind, in forming a spiral twist ; then they are reflected 

 from below upwards, to enter the inferior extremity of the ventricles, on the 

 internal face of the proper fibres of which they spread and ascend to the fibrous 

 zones at the base of the heart, where they terminate. Some of these reflected 

 fibres are disposed in relief, to constitute the columnse carnese, and reach the 



Fig. 356. 

 Fig. 355. 



ANASTOMOSING MUS- 

 CULAR FIBRES OP MUSCULAR WHORL AT THE POINT OF THE 

 HEART. HEART. 



1, Vortex or whorl with small opening in the 

 middle; 2, auricle; 3, intercrossing of the 

 anterior and posterior unitive or uniting 

 fibres. 



auriculo-ventricular zones through the medium of the chordfe tending that 

 directly connect these fibrous rings with the summits of the muscular pillars. 



All the fibres do not reach the point of the heart to ascend to the fibrous 

 zones ; a certain number are reflected at different heights in the layer they form, 

 and Gerdy has compared them to a number of horns placed one within the 

 other, and flattened as are the walls of the ventricles. 



Such is the general disposition of the unitive fibres of the ventricles : and it 

 will be seen that they form a superficial and a deep or reflected plane, between 

 which are comprised the fasciculi proper to each ventricular cavity. 



The unitive fibres of the ventricles, therefore, form collectively a kind of 

 figure 8, the smallest loop of which is at the point of the heart ; there the fibres 

 are heaped together, leaving in the centre of the loop a very small space, through 

 which it is possible to pass a probe into the ventricle, without piercing anything 

 but the external and internal serous membranes of the organ. 



2. Fibres of the Auricles. — The fibres of the auricles are either common 

 to the two cavities, or proper to each. 



