128 



THE ANATOMY OP THE HOESE. 



surface of the valve is convex, and, during contraction of the ventricle, 

 it is directed to the blood-stream ; the other is concave, and directed to 

 the wall of the artery, which, opposite each segment, forms a pouch — 

 the sinus of Valsalva. When the ventricle has ceased to contract, the 

 elastic recoil of the artery forces the blood against the concave side of 

 the segments, and carries them inwards till they meet and completely 

 close the opening. The blood is thus propelled along the pulmonary 

 arteries to the lung, where, in the capillary plexus on the walls of the 

 air-cells, it is purified. The purified fluid is then carried from the lungs 

 by the pulmonary veins, which pour it into the left auricle of the heart. 

 Directions. — The cavity of the left auricle is to be exposed by an 

 incision from the right to the left pulmonary veins, and by another 

 from the first to the point of the appendix. 



The Cavity of the Left Auricle is smaller than the right, but, like 

 it, consists of a simts venosus and an ear- 

 shaped appendage — the auricula. The pul- 

 monary veins open on the roof of the 

 sinus venosus ; and most commonly they 

 have four openings — two from each lung, 

 but they may have as many as eight. 

 They are not provided with valves. The 

 auricula and adjacent part of the sinus 

 venosus show musculi pectinati similar to 

 these of the right auricle. In the floor of 

 the cavity is the left auriciilo-ventricular 

 opening, by which, on contraction of the 

 auricle, the blood is passed into the left 

 ventricle. 



Directions. — The left ventricle should be 

 opened by an incision similar to that used 

 on the right side. The point of the scalpel 

 should be passed through the wall of the 

 ventricle near the upper end of the left 

 ventricular furrow, and the incision should 

 be carried down the left side of the 



THE HEABT (Ellis). , • 1 J J.1 1 ,1 



. „. , . ventricle, round the apex, and up the 



y veins ; i. Bight ' . . 



■"---'--'-•■— right side to within a short distance of 

 the auriculo-ventrioular groove, the cut 

 being made near the septum, to which the 

 ventricular furrows will serve as a guide. 



The Cavity of the Left Vbnteiclb is longer than the right, and is 

 almost conical in shape, the base being at the auriculo-ventricular 

 opening. On transverse section, it gives an oval or nearly circular 

 outline, the septum, as well as the wall of the ventricle, being concave 



Fig. 10 



Diagram of the two Cavities of 

 the left side of 



k. Left pulmonary 

 pulmonary veins ; o. Remains of fora^ 

 men ovale ; I. Left auriculo-ventiic 

 ular opening ; m. Auricular appendix 

 11. Aperture of the aorta. 



