The frog: an introduction to anatomy, histology, and embryology . nical in shape, with the apexpointing backwards,iii. The truncus arteriosus is a cylindrical body arisingfrom the right anterior border of the ventricle,and running obliquely forwards across theauricles. THE VEINS 25 lAft up the ventricle and twin its apex forwards so as toexpose the sinus venosus. iv. The sinus venosus is a thin-walled sac, lying dorsalto the ventricle and behind the auricles; itreceives the three large vense cavae. 2. The pulsation of the heart. a. Note that the contractions of the heart continue some time aft
The frog: an introduction to anatomy, histology, and embryology . nical in shape, with the apexpointing backwards,iii. The truncus arteriosus is a cylindrical body arisingfrom the right anterior border of the ventricle,and running obliquely forwards across theauricles. THE VEINS 25 lAft up the ventricle and twin its apex forwards so as toexpose the sinus venosus. iv. The sinus venosus is a thin-walled sac, lying dorsalto the ventricle and behind the auricles; itreceives the three large vense cavae. 2. The pulsation of the heart. a. Note that the contractions of the heart continue some time after the frog has been killed, or even after theheart is completely removed from the body. b. Note the character of the hearts pulsations : a regularly alternating series of contractions and dilatations. c. Note further that in each contraction or systole of the heart all four divisions of the heart contract, but notsimultaneously. The sinus venosus contracts first,then the two auricles, then the ventricle, and finallythe truncus arteriosus. B. The Veins. Bt, Fig. 4.—Diagrammatic figure of the venous system of the frog,from the right , ?. L ^ a, stomach ; , mtgior abdominal vein; b, bladder; ^.ij. brachiaLvein ; , cloacal aperture j^.w, cardiac vein; d, large intestine ;e, liver ; , external ]nplgr y^in ; f,v, femoral vein ; g, gall-bladder;h, spleen ; , P0Ste-iT R^p, ? : , iTinnininate Y(;in ; , jntRrnaljiipnlpr vpin ; , leftgelvis_jein; , TnTiiciiln-cutanenns vein ;0, kidney-^.w, hepatic portal vem ; , right pelv^ vein ; rightrenal pqrtaL-itein: j. suihs venosus : , sciyic vein ; , ffihrlflvi^nvein: t, tongue; , truncus arteriosus; », right auricle; v, ven-tricle ; , vesical veins. 26 THE VASCULAR SYSTEM OF THE FROG The veins should be dissected before the arteries, because, asa rule, they lie nearer the surface and are therefore met withfirst. The veins are further distinguished from the arteries bytheir larger size and
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbiology, bookyear1896
