COLUMNS CARNEY. 535 



brane, strengthened by a thin layer of fibrous tissue. They are con- 

 nected by their base around the auriculo- ventricular opening ; and by 

 their sides and apices, which are thickened, they give attachment to a 

 number of slender tendinous cords, called chordae tendineae. The 

 chordae tendinece are the tendons of the thick muscular columns (co- 

 lumnae carnece) which stand out from the walls of the ventricle, and 

 serve as muscles to the valves. A number of these tendinous cords 

 converge to a single muscular attachment. The tricuspid valves pre- 

 vent the regurgitation of blood into the auricle during the contraction 

 of the ventricle, and they are prevented from being themselves driven 

 back by the chordae tendineae and their muscular attachments. 



This connection of the muscular columns of the heart to the valves 

 has caused their division into active and passive. The active valves 

 are the tricuspid and mitral ; the passive, the semilunar and coronary. 

 Mr. King, of Guy's Hospital, has made the tricuspid valves the 

 subject of careful investigation, and has recorded his observations in 

 the Guy's Hospital Reports.* The valves consist, according to Mr. 

 King, of curtains, cords, and columns. The anterior valve or curtain is 

 the largest, and is so placed as to prevent the filling of the pulmonary 

 artery during the distension of the ventricle. The right valve or 

 curtain is of smaller size, and is situated upon the right side of the 

 auriculo- ventricular opening. The third valve, or "fixed curtain,' 1 '' 

 is connected by its cords to the septum ventriculorum. The cords 

 (chordae tendineae) of the anterior curtain are attached, principally, to 

 a long column (columna carnea), which is connected with the " right or 

 thin and yielding wall of the ventricle." From the lower part of this 

 column a transverse muscular band, the " long moderator band," is 

 stretched to the septum ventriculorum or " solid wall" of the ventricle. 

 The right curtain is connected, by means of its cords, partly with the 

 long column, and partly with its own proper column, the second 

 column, which is also attached to the " yielding wall" of the ven- 

 tricle. A third and smaller column is generally connected with the 

 right curtain. The "fixed curtain" is named from its attachment to 

 the " solid wall" of the ventricle, by means of cords only, without 

 fleshy columns. 



From this arrangement of the valves it follows, that if the right 

 ventricle be over-distended, the thin or "yielding wall" will give 

 way, and carry with it the columns of the anterior and right valves. 

 The cords connected with these columns will draw down the edges 

 of the corresponding valves, and produce an opening between the 

 curtains, through which the superabundant blood may escape into 

 the auricle, and the ventricle be relieved from over- pressure. This 

 beautiful mechanism is therefore adapted to fulfil the " function of a 

 safely valve." 



The Columnce cameos (fleshy columns) is a name expressive of the 

 appearance of the internal walls of the ventricles, which seem formed 



* " Essay on the Safety Valve Function in the Right Ventricle of the Human 

 Heart," by'T. W. King. Guy's Hospital Reports, vol. ii. 



