PARTS OF THE HEART. 331 



882. Valva semilunaris, vlv. slmr.One of the six semilunar 

 or sigmoid valves (Fig. 92, 94, 96, 100). The mouths or bases of 

 the aorta and A. pulmonalis are guarded each by three of these 

 valves. Their free borders are nearly even, and naturally look 

 peripherad. Like the sinuses of Valsalva, which they partly cover, 

 the three aortic valves are approximately dorsal, dextral and sinis- 

 istral respectively, while those of the pulmonary artery are approx- 

 imately ventral, dextral and sinistral. 



883. Valva Thebesii (az.\ vlv. Thb. The valve of Thebesius. 

 This name has been applied to the semilunar valve at the entrance 

 of the V. cardiaca through the sinus coronarius into the right 

 auricle (Quain, A, II, 246). It is easily seen in the cat. 



884. Valva tricuspis, vlv. trc. One of the three tricuspid 

 valves (Fig. 92, 93, 94, 96, 97, 99). As in man, one of these light 

 auriculo- ventricular valves is nearer the septum, while the other two 

 are, approximately and relatively, dorsal and ventral. There is 

 considerable variation in their form. Usually the free border is quite 

 irregular, but in the preparation from which Fig. 94 was taken, 

 the free border is even and the chordae tendinese are attached at the 

 lateral edges. 



885. Vena azygos (az.\ V. az. The azygous vein (Fig. 91, 99, 

 101, 920). This vein opens into theprcecava about 1 cm. peripherad 

 of its junction with the right auricle. 



886. Vena cava (az.\ V. cv The adjective cava is applied to 

 either of the two great veins through which the impure blood is 

 brought from the organs in general to the right auricle. It is more 

 commonly employed for the longer and larger of the two, which 

 traverses the abdomen and penetrates the diaphragm. By Owen 

 (A) the two are designated as the postcaval and prcecaval veins. 

 The vessels are so large, so important and so often mentioned, that 

 we have ventured to omit the vena and to designate them as simply 

 prcBcava and postcava. In the diagram (Fig. 92) the single Vena 

 cava represents both prcecava and postcava. 



887. Vena cardiaca, V. crd. One of two or more cardiac or 

 coronary veins (Fig. 91, 92). The blood which has traversed the 

 tissues of the heart itself is returned to the right auricle by one 

 large and one or more smaller veins, all of which open into a small 

 sinus (sn. coronalis\ which has been described above ( 877). 



888. Venae pulmonales The pulmonary veins (Fig. 91, 92). 



