26 



BOYINE OBSTETKICS 



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 blood flows. 



A, Heart; B, umbilical opening; G, portion of the chorion. 1, Anterior aorta; 2, pos- 

 terior aorta; S, anterior vena cava; U, posterior vena cava; S, duct of Botalli; 

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

 but was necessary in order to demonstrate it) ; 6, umbilical arteries; 7, umbilical 

 vein; 7', some of its branches; S, portal vein; 5, ductus venosus; 10, portal veins; 

 11, pulmonarj; artery; 11', some of its branches; is, pulmonary veins; is, tuber- 

 culum Loweri; 14, chorion papillae. 



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- 



