326 OF THE GROWTH, &c. 



and Is produced by the fermentation of tlie 

 matters they contain *. 



The lungs of the foetus, having no motion, 

 receive no more blood than is fufficient for 

 their nourifhment and growth: Another paflage, 

 therefore, is open for its circulation. The blood 

 in the right auricle of the heart, inftead of paf- 

 fmg into the pulmonary artery, and, after cir- 

 culating through the lungs, returning into the 

 left auricle by the pulmonary vein, palTes dired:- 

 ly from the right to the left auricle, through an 

 aperture called the foramen O'uale, which is in 

 the partition of the heart that feparates the two 

 auricles: The blood then enters the aorta, by 

 the ramifications of which it is diftributed to 

 every part of the body ; it is then taken up by 

 the numerous branches of the veins, which gra- 

 dually unite into one trunk, called the vena cava, 

 that terminates in the right auricle of the heart. 

 The blood contained in this auricle does not all 

 pafs through the foramen ovale ; part of it e- 

 fcapes into the pulmonary artery, but it enters 

 not into the body of the lungs ; for there is a 

 communication between the pulmonary artery 

 and the aorta, by an arterial canal which leads 

 immediately from the one to the other. It is 

 by thefe means that the blood circulates in the 

 ' foetus, without entering the lungs, which it 

 does in children, in adults, and in all animals 



who refpire. 



It 

 * See Vegetable Statics, chap. 6. 



