A treatise on zoology . he right and left ductusCuvieri and the hepatic veins join to enter the sinus venosus. Thisleads into a thin-walled atrium, opening into a muscular thick-walled ventricle. There are two sinu-atrial and two atrio-ventricular valves. The ventricle is prolonged forwards into acontractile conns arteriosus, leading to the ventral aorta (Stohr[426], Boas [38-39], Kose [373]). Inside the conns are rows ofsemi-lunar valves (Fig. 69). In the more specialised Teleostei thebase of the aorta is swollen into a non-contractile bulbus, and theconus is reduced to a narrow strip support
A treatise on zoology . he right and left ductusCuvieri and the hepatic veins join to enter the sinus venosus. Thisleads into a thin-walled atrium, opening into a muscular thick-walled ventricle. There are two sinu-atrial and two atrio-ventricular valves. The ventricle is prolonged forwards into acontractile conns arteriosus, leading to the ventral aorta (Stohr[426], Boas [38-39], Kose [373]). Inside the conns are rows ofsemi-lunar valves (Fig. 69). In the more specialised Teleostei thebase of the aorta is swollen into a non-contractile bulbus, and theconus is reduced to a narrow strip supporting only one row ofvalves (p. 363). As a primiti^^e type of circulation we may take that of aSelachian (Hyrtl, Balfour [27], Hoehstetter [214-15], Dohrn[114], Rabl [336], Parker [314-15]). The median ventral aorta,morphologically a forward prolongation of that longitudinal ventral subintestinal vessel of which the heart itself is a specialisedportion (p. 26), and like that vessel developing from originally paired PISCES. Ill- - OiS - ?-- .2 S 5~ fe ° 5 ?;.$ ^ T & a, C ,2 J ?^-?e OSS- I =1 ^^ -- ^ C t S K O £ «^ 3 S >uo ° o o ? - a> -e; -3j--^ 2 1° VASCULAR SYSTEM rudiments (Mayer [297fl]),runs forward below thebranchial skeleton (Fig. 71). Itprovides five afferent branchialarteries, the first of whichpasses up the hyoid archto supply its posterior hemi-branch. These afferent vesselsand the efferent vessels arepartially derived from, andreplace, the embryonic com-plete aortic arches, six inmimber, running up the man-dibular, hyoid, and succeedingfour branchial arches. Thepaired rudiments of the dorsalaorta unite to form a singlemedian vessel behind ; but infront they diverge and joinagain below the brain to formin the embryo a completecircle, the circulus cephalicus(Fig. 72). It is this regionwhich receives the efferent orepibranchial vessels. The con-tinuity of the circulus is usu-ally interr
Size: 1182px × 2113px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
