26 



BOVINE OBSTETRICS 



as the pulmonary circulation does in the lungs. The venous 

 blood in the placenta gives off carbon and takes up oxygen. 

 This process is the so-called placental respiration. The blood 

 oxygenated in the placenta reaches the foetus at the umbilical 



Fig. 10. — Schematic Sketch of the Foetal Circulation of a Calf. 



The arrows indicate the direction in which the hlood flows. 



A, Heart; B, umbilical opening; C, portion of the chorion. 1, Anterior aorta! .. pos- 

 terior aorta; .;. anterior vena cava; U, posterior vena cava; . dnct of Botalli; 

 .'', part of Botalli's duct posterior to the heart (sketched somewhat too long, 



but was necessary in order to demonstrate it); '■', umbilical arteries; 7, umbilical 

 vein; ?', some of its brandies; 8, portal vein; ''.ductus venosus; 10, portal veins; 

 11, pulmonary artery; W, some of its branches; U, pulmonary veins; • . tuber. 

 culuin Loweri; II,, chorion papilla. 



ring by the two umbilical veins. Within the umbilical ring 

 the two veins coalesce to form one vessel, which Leads to 

 the liver {porta hepatica), first giving off a branch (ductus 

 Arantii) emptying into the posterior vena cava. The remain- 



