CHAPTER XIV. 



Tab. XXIX. — foramen ovale, and ductus arteriosus. 



Fig. 1. A view of the foetal heart ; a, the ascending, 6, the 

 descending vena cava ; c, the right auricle ; rf, e, /, mark the 

 elevated ring of the foramen ovale, or the opening between 

 the two auricles. 



Fig. 2. The foetal heart ; a, the pulmonary artery ; 6, 6, its 

 branches ; c, the ductus arteriosus, or canal for transmitting 

 the blood into, d, the aorta. As the lungs are useless in the 

 foetus, unless as a " prospective contrivance," the heart has to 

 carry on a single circulation only : the free communication 

 between the two auricles identifies them as one cavity ; and 

 the ventricles also force the blood into one vessel, the aorta. 



