128 



THE ANATOMY OP THE HORSE. 



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 ai-tery, which, opposite each segment, forms a pouch — 

 the sinvs 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 simis 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 leji auric ulo-ve7itricular 

 opening, by which, on contraction of the 

 auricle, the blood is passed into the left 

 ventricle. 



Directiojis. — The left ventricle should be 

 opened by an incision similar to that used 

 on the right side. The point of the scalpel 

 shovild be passed through the wall of the 

 ventricle near the upper end of the left 

 ventricular furrow, and the incision should 

 be carried doAvn the left side of the 

 round the apex, and up the 



Fig. 10 



Diagram ok the two Cavitie 



THE LEFT SIDE OK THE HEART (Ellis). , . ■, 



, ^ . , • • T,- 1 / ventricle, 



k. Left pulmonary veins ; i. Right ' . 



pulmonary veins ; o. Remains of fora- right sidc tO WlthlU a short dlStaUCe Of 



men ovale; «. Left auriculo-ventiic- ° . , , • i ,i 



ular opening ; m. Auricidar appendix ; the auriCUlo-VeiltriCUlar grOOVC, the CUt 



n. Aperture of the aorta. ^^.^^ ^^^^ ^^g.^^. ^^^ geptum, tO which the 



ventricular furrows will serve as a guide. 



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

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

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

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



