THE FORM CHANGES OF THE HEART IN SYSTOLE 



163 



the right, a condition which conforms with the much heavier work to be done 

 by the former. In fact the outer wall of the right ventricle is formed for the 

 most part of fibers which come 

 from the left. To a certain ex- 

 tent therefore the right ven- 

 tricle may be looked upon as 

 a cleft in the wall of the left, 

 as shown in Fig. 51. 



With regard to the struc- 

 ture of the ventricles the fol- 

 lowing is worthy of mention : 

 From the fibro-tendinous rings 

 at the base of the left ventricle, 

 and from the muscular sides of 

 the aorta superficial fibers pass 

 obliquely downward to the apex 

 of the heart, enter for the 

 most part the vertex of the left 

 ventricle and double round into 

 its interior, to be inserted 

 either into the papillary mus- p IG 51. Cross-section through a fully contracted 

 cles and chordae tendinese, or human heart at the junction of the upper and 



into the atrio-ventricular ring. middle thirds, after Krehl. 



The two layers thus formed 



ate separated by a median layer, which, when isolated by a special method 

 of preparation, has the form of a muscular cone. It is connected also by many 

 fibers with the outer and inner layers. The fibers of this median part describe 

 loops, which, not having any tendinous connections, return to their starting point 

 (Fig. 52). It is obvious that this strongly developed median layer must play a 



prominent part in the contrac- 

 tion of the left ventricle. 



The synchronism of con- 

 traction of the two ventricles 

 naturally depends on the fact 

 that the muscular fibers are 

 in part common to both ven- 

 tricles. Nevertheless various 

 observations indicate that this 

 synchronism is not an absolute 

 one, but that each ventricle 

 possesses a certain physiolog- 

 ical independence (Knoll). 



B. THE FORM CHANGES OF 

 THE HEART 



In diastole the form of the 



FIG. 52. Layer of fibers in the left ventricle of the Ventricles of an empty heart 



human heart which have no tendinous insertions. Outside the body depends in the 



The more external and more internal layers have main n the in w ^ c ^ 



been removed. The outline of the entire heart is , V i 



shown. After Krehl. the J are supported, whereas 



