An introduction to the study of embryology / by Alfred C. Haddon.

  • Haddon, Alfred C. (Alfred Cort), 1855-1940.
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: An introduction to the study of embryology / by Alfred C. Haddon. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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    vein is formed. Although the allantoic vein disappears before hatching, the caudal and posterior pelvic veins are connected with the portal vein in the adult by the coccygeo-mesenteric vein (fig. 169, C, cy, m). In Mammals the two primitive anterior abdominal (allantoic) veins are very early developed, and unite in front with the vitelline vein. The right allantoic vein (fig. 171, B, u), like the right vitelline vein {0'), soon disappears. The long common trunk of Fig. 170.—Diagram of the Ar- rangement OF THE Principal Vessels in a Human Fcetus. [From Clans after Ecker.] Ao. aortic trunk; Am. amnion; Aod. dorsal aorta; Az. azygos vein ; C. anterior cardinal vein; Cc. com- mon carotid; C'e. external carotid; Ci. internal carotid; D. ductus ven- 08US Arantii; DC. ductus Cuvieri; Az L>v. vitelline duct; H. ventricle ; L. liver; N. umbilical vesicle (yolk-sac); O. vitelline (omphalo-mesenteric) ar . j- tery; O'. vitelline vein' P. lung; ■'^ S. subclavian artery; U. allantoic (umbilical) arteries with their pla- cental ramifications, U; U'. aUantoio vein; V. auricle; V.c. vena cava inferior; Vp. portal vein; i, 2, 3, 4, 5. the arterial arches—the persistent left aortic arch is not visible. the (left) allantoic and vitelline veins (ductus venosus) passes through the liver. In its passage through the liver, according to Kolliker, the ductus venosus gives off branches near its entrance, and receives branches from the anterior end of the liver (fig. 171, b). The main duct, unlike what occurs in the Sauropsida, persists through- out life as the ductus venosus Arantii (fig. 171, D, ^). When the placenta is developed, the allantoic circulation be- comes extremely important. The vitelline vein, on the other hand, is greatly reduced, and, with the larger mesenteric vein, it con- stitutes the portal vein. Later the portal vein (fig. 171, d, ^) enters one of the venae advehentes of the allantoic vein (jp'). The vena cava inferior and the ductus venosus at first unite together and enter the heart by a common trunk (fig. 171, A, a, Z) Owing to the increased size of the former, the venaa reheventes or hepatic veins open into it, and not into the ductus venosus. The