ON THE MOTIONS AND SOUNDS OF THK HEART. 277 



the margin of the auriculo-ventricular opening which corresponds 

 to the portion of the ventricle not formed by the septum, and 

 may be desci'ibed, with reference to the smaller flap, as being 

 placed externally to it, and to its right side : the smaller flap is 

 connected to that portion of the margin of the opening which 

 corresponds to the septum, and is, with regard to the larger flap, 

 internal and to the left side. When these flaps are in contact 

 with each other during the ventricular systole, the line of their 

 junction is vertical, being very nearly at right angles to the ana- 

 logous line as described in the mitral valve. 



The papillary muscles of the mitral valve vary in number in 

 different subjects, but there are always two larger than the others, 

 arising from the posterior wall of the ventricle, about midway 

 between the apex and the base, one of which is situated close to 

 the septum, and the other at the external edge or part of the 

 posterior wall. They are somewhat flat-shaped, and are nearly 

 parallel to each other and to the axis of the ventricle. Each 

 of these papillary muscles terminates in two or three papillae of 

 nearly equal length, and whose summits are about one-fourth 

 of an inch asunder. From these summits proceed, in a radiating 

 form, a great number of tendinous cords, which are distributed 

 to the flaps of the valve in the following manner : those cords 

 which arise from the superior papilla on each side are connected 

 to the superior or larger flap ; those from the papilla on each 

 side, situated between the superior and inferior, are distributed 

 partly to the larger flap, and partly to that portion of the valve 

 where the lai'ger and smaller flaps are conjoined; and the cords 

 arising from the lowest papilla on each side are connected chiefly 

 to the smaller or inferior flap. Besides the two papillary mus- 

 cles just described there are others smaller, which arise from the 

 posterior wall of the ventricle, nearer its base, at a situation 

 corresponding to the attachment of the smaller flap, to which 

 flap the tendons proceeding from these muscles are distributed. 



In the I'ight ventricle the papillary muscles connected with 

 the larger flap are three or four in number, and arise near the 

 apex of the ventricle by footstalks proceeding generally both 

 from the septum and from the external wall of the ventricle. 

 They are somewhat flat in shape, nearly parallel in their direc- 

 tion to the axis of the ventricle, and placed at intervals of half 

 or three quarters of an inch from each other, measured along the 

 external wall of the ventricle, M'hich is of a curved form, and 

 seems to be wrapped round the septum. From the papillae by 

 which these muscles are terminatedproceed a number of tendinous 

 cords, which are distributed in a radiating manner to the surface 

 and margin of the larger flap. The superior part of this mar- 



