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VETERINARY PHYSIOLOGY 



4. Gestation and Delivery 



The child remains in the uterus for nine months, and at the 

 end of that period it is expelled during labour. Labour may be 



l.V. 



FIG. 177. Scheme of Circulation in the Foetus, u.v., umbilical vein ; d.v., 

 duotus venosus ; p.v.e., inferior vena cava pouring blood through the right 

 auricle and through the foramen ovale, f.o., into the left heart ; a.v.c., 

 superior vena cava bringing blood from the head to pass through the right 

 side of the heart, and through theductus arteriosus, d.a. ; pt.v., portal vein. 

 The degree of impurity of the blood is indicated by the depth of shading. 



divided into three stages. In the first stage the uterus passes 

 into contractions at intervals, and the lower part or cervix is 

 dilated. In the second stage the contractions become stronger, 

 and with the help of the contractions of the abdominal muscles, 

 the young are expelled through the vagina either enclosed in 



