THE HEART. 



591 



Kig. 353. 



anterior, the other posterior, siiuulatiiit,' in their outline the two faces of a 

 bishop's mitre. The anterior festoon is the largest, and is attached to tiic limit 

 of the two orifices, isolating from the ventricular cavity a diverticuUim which 

 corresponds, in every respect, to the pulmonary infundibuium. Tlie posterior 

 festoon is applied to the walls of the ventricle. Between these two then; are 

 usually two secondary festoons, making up the total number to four ; fre juently 

 tliere is an accessory fold, situated on the right side, and fairly developed ; the 

 valve is then tricuspid, like that of the right ventricle. Sometimes two of these 

 rudimentary folds are found on the left side — making five festoons in all, The 

 aortic opminij — so named because it constitutes the origin of the aorta — is placed 

 in front and to the left of the auriculo-ventricular opening, from which it is only 

 separated by a tliin muscular spur, 

 to which is attached the adherent 

 border of the great festoon or curtain 

 of the mitral valve. It does not 

 differ in anything from the pulmonary 

 opening, and, like it, is provided with 

 three sigmoid (or semilunar) valves. 



Left Auricle. — As in the right 

 auricle, this forms a kind of lid above 

 the auriculo-ventricular opening. 

 Smooth behind, in front, inwards and 

 outwards, its cavity presents a reticu- 

 lated cul-de-sac, which occupies the 

 auricula ; and a superior wall, also 

 reticular, having from four to eight 

 Orifices — the openings of the pul- 

 monary veins. These orifices have 

 no valves. {Carnen. columnce of the 

 third kind are also present, but chiefly 

 between the two posterior pillars ; 

 small ones are very numerous on the 

 borders and summit of the ventricle. 

 The columns of the second order are 

 simple or ramous, and pass from the 

 angles of union of the walls and the 

 point of the cavity ; others on the posterior wall go to the borders and the 

 interval between the two pillars. The most remarkable are bands extending from 

 one wall to the other, the two principal of which are long, strong, and ramous ; 

 they are fixed, on the one side, to the centre of the great posterior reliefs, and 

 ascend to be implanted, on the other side, into the middle of the anterior wall.) 



I.EIT rAVnilvS OF HEART LAID OPEN. 



1, Cavity of left aiiricli'; 2, cavity of appeudix 

 auricula;; 3, opening of two right pulmonary 

 veins ; 4, sinus into which left pulmonary veins 

 open; 5, left pulinonai-y veins; 6, auriculo-ven- 

 tricular opening ; 7, coronary vein lying in 

 auriculo-ventricular groove; 8, left ventricle; 

 9, 9, cavity of left ventricle, a, Mitral valve, 

 its curtains connected by chordflc tendinae to 6, 6, 

 columnce carne.x ; c, c, fixed columnea' cnrna; on 

 inner surface of ventricle ; i, point of appendix of 

 right auricle. 



4. Steucture of the Heart. 



Preparntinn. — Before proceeding to dissect the musctdar fibres of the heart, it is indis* 

 pensable to keep that visous in boiling water for half or three quarters of an hour. It should 

 then be immediately immersed in cold water, to prevent the desiccation of the serous membrane 

 covering it, and which must be at once removed. The furrows should then be cleared of their 

 Vessels and fat; this renders the superficial muscular fibres very apparent. The same result 

 may l>e attained by immersing the heart in vinegar or dilute hydrochloric acid. To isolate the 

 ventricles and U'litive fibres from each other, the following proceiiure may be a<lopted : After 

 removing the auricular mass and dissecting the fibrous rings, the unitive fibres around these 



