198 



THE BLOOD VASCULAR SYSTEM 



portions of the myocardium. At their valvular attachment the fibrous 

 bundles of the chordae tendineae turn almost at right angles, and spread 

 out, in a somewhat radial manner, to become continuous with the dense 

 fibrous tissue which forms the interior of the valve. 



FIG. 214. RADIAL SECTIONS OF THE MITRAL VALVE, FROM THE HEART OF A MAN. 



A, from the base of the valve showing the extension into it of cardiac muscle fibers 

 from the wall of the heart; B, from the mid-region of the valve, a, auricular endo- 

 cardium; 6, muscle fibers; c, dense fibrous tissue; d, ventricular endocardium. Hema- 

 tein and eosin. Photo. X 800. 



Columnae Carneae. The columns? carneae are colnmelliform projec- 

 tions of the myocardium into the ventricular cavity. They consist of 

 cardiac muscle fibers, largely of the Purkinje fiber variety, which are dis- 

 posed in their long axis, and are covered by reflections and reduplications 

 of the endocardium. The irregular contour of the ventricular cavities 

 appears to be entirely due to the projecting columnge carneas. 



