332 ANATOMICAL TECHNOLOGY. 



Near the left auricle tliese form three wholly distinct groups of two 

 each, which from their position may be called dextral, sinistral and 

 intermediate or dorsal. 



Disregarding the smaller subdivisions, some of which are not 

 represented in the figures, each group consists of two trunks which 

 open into the auricle by a common sinus of varying depth. 



The intermediate and the sinistral sinus are indistinctly seen in 

 Fig. 95 at the ends of the lines drawn from the abbreviation W., 

 but the separate orifices of the veins do not appear. The dextral 

 sinus could not be shown in the same figure, but its position is 

 indicated approximately by the s of the word sex^titm. 



When traced to the lungs, it is found that the dextral and sin- 

 istral groups come from the right and left lungs respectively, but 

 that of the two large constituents of the intermediate, the one nearer 

 the right comes from the lung of that side, and the other from the 

 left. 



In man, there are usually two pulmonary veins on each side, 

 opening independently into the auricle. 



§ 889. Ventriculus dexter, 'ent. dxt. — The right or pulmonary 

 ventricle (Fig. 91, 92, 93, 94, 97, 98, 99).— This is not only, as its 

 name implies, relatively dextral in position, but also, in the natural 

 attitude of the organ, somewhat more ventral than the left ventricle. 

 Its walls are markedly thinner than those of the left, and its cavity 

 does not so nearly reach the apex of the organ. The ental surface 

 of its walls presents numerous elevations and depressions. In addi- 

 tion to the columncB carnecE and the trahecula tenuis, there are 

 many muscular trabeculse passing obliquely from one part of the 

 wall to another, forming a sort of coarse network. The sinistro- 

 cephalic corner of the ventricle is devoid of reticulations, and is 

 prolonged as the conus arteriosus (§ 866). 



§ 890. Ventriculus sinister, vnt. sin.— The left or systemic ven- 

 tricle (Fig. 91, 92, 93, 94, 97, 98, 99).— Tliis is not only sinistral, 

 but also, relatively, somewhat more dorsal in position in the natu- 

 ral attitude of the heart. Its lateral walls are 2-3 times as thick as 

 those of the right ventricle, and its cavity reaches more nearly to 

 the apex of tlie organ. In the contracted state of the heart, the left 

 ventricle occupies the more space on account of the greater thick- 

 ness of the walls (Fig. 93) ; but the thinner walls of the right yield 

 more to the pressure of an injection, and its cavity generally appears 

 more capacious (Fig. 91, 97, 98). It presents two large columnae 



