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507 



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other posterior, simulating iu tlieir outline the two faces of a bishop's 

 e. The anterior festoon is the largest, and is attached to the limit of 



Fig. 262. 



provided with a circular membrane, the mitral (or bicuspid) valve, because it is 

 cut into several festoons, of which two arc the principal: the one anterior, 

 the 

 mitre 



the two orifices, isolating from 

 the ventricular cavity a diver- 

 ticulum which corresponds, in 

 every respect, to the pulmonary 

 infuudibulum. The posterior 

 festoon is applied to the walls 

 of the ventricle. Between these 

 two there are usually two second- 

 ary festoons, making up the 

 total number to four ; fre- 

 quently there 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 opening, so named 

 because it constitutes the origin 

 of the aorta, is placed in front 

 and to the left of the auriculo- 

 vuntricular opening, from which 

 it is only separated by a thin 

 muscular spur, to which is at- 

 tached 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 valves. 



LEFT AUKICLE. As in the right auricle, this forms a kind of cover 

 above the auriculo-ventricular opening. Smooth behind, in front, inwards 

 and outwards, its cavity presents a reticulated cul-de-sac, which occupies tho 

 appendix auriculae ; and a superior wall, also reticular, having from four to 

 eight orifices, the openings of tho pulmonary veins. These orifices have no 

 valves. (Carneio column of the third kind are also present, but chiefly 

 between tho two posterior pillars; small ones are very numerous on the 

 borders and summit of tho ventricle. Tho columns of tho second order are 

 simple or wmous, and pass from the angles of union of tho walls and tho 

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

 interval between tho two pillars. Tho most remarkable are bauds extending 

 from one wall to tho other, tho two principal of which are long, strong, and 

 ramous ; they are fixed, on tlie one side, to tho centre of the great pow 

 reliefs, and ascend to be implanted, on tho other side, into tho middle of 

 the anterior wall.) 



4. Structure of the Heart. 



'ration. Before proceeding to dism-t tin- uniM-ular film's >!" tin heart, it is 

 indbpeOMlde to keep th:it vi.icna in boiling water fur liuif or tl.i "t'j'M Inmr. 



It -liuiil.l tin 11 l iiiiin. ,lial< ly innin rs. il in mM \viit< r. " prest lit th- <l. .-ieralij -i of th- 



LEFT CAVITIES OF HEART LAID OPEN. 



1, Cavity of left auricle ; 2, Cavity of appendix 

 auriculae ; 3, Opening of two right pulmonary 

 veins ; 4, Sinus into which left pulmonary veins 

 open; 5, Left pulmonary veins; 6, Auriculo-ven- 

 tricular opening ; 7, Coronary vein lying in 

 auriculo-ventricular groove ; 8, Left ventricle ; 

 9, 9, Cavity of left ventricle. '(, Mitral valve, 

 its curtains connected by chordae tcndina- to b, 6, 

 Columnae carneae ; c, c, Fixed columnar carnae 

 on inner surface of ventricle ; i, Point of appendix 

 of right auricle. 



