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CHAPTER XIV. 
Plate XXIX. — foramen ovale, and ductus arteriosus. 
Fig. 1. A view of the foetal heart; a, the ascending, 6, the de¬ 
scending vena cava; c, the right auricle; d, e, f 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, b, 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,” t#e heart has to cany on a single cir¬ 
culation only: the free communication between the two auricles 
identifies them as one cavity; and tne ventricles also force the 
blood into one vessel, the aorta. 
jLH 
