Lesson xxxix.] OF THE BLOOD. 299 



pulmonary veins, is received into the left auricle 

 of the heart, and from thence it is pushed into 

 the left ventricle 5 which, being thus filled, con- 

 tracts itself, and drives the Blood with great rapi- 

 dity to all the parts of the body, and from them 

 it returns again through the veins into the right 

 auricle of the heart, as before. 



It is very remarkable, that we have here a dou- 

 ble Circulation : one, from the right ventricle, 

 through the lungs, to the left auricle of the heart, 

 in order to convert the chyle into Blood, and 

 finally prepare it for the nourishment of the ani- 

 mal ; the other, from the left ventricle, through 

 the whole body, to the right auricle of the heart, 

 which serves to apply that nourishment to every 

 part, besides various other purposes. 



But to proceed Of these four muscular cavi- 

 ties, the two auricles are contracted at the same 

 instant, while the two ventricles are dilated j the 

 ventricles, in their turn, are contracting them- 

 selves at the very instant that the auricles are di- 

 lating. The arteries, in like .manner, beat in 

 alternate time with the ventricles of the heart. 



The nerves, as well as the veins and arteries, 

 act their part in this rotation of the Blood; for 

 if the eighth pair of nerves which proceeds from 

 the brain to the heart be bound up, the motion of 

 the heart immediately languishes, and soon ceases 

 entirely. 



Thus we have a species of perpetual motion, 

 which none but a Being of infinite wisdom and 



power 



