•)4 OF THE VESSELS 



tricle will at least contain one ounce of blood. The heart 

 contracts four thousand times in one hour ; from which it 

 follows, that there passes through the heart, every hour, 

 four thousand ounces, or three hundred and fifty pounds of 

 blood. Now the whole mass of blood is said to be about 

 twenty-five pounds, so that a quantity of blood equal to the 

 whole mass of blood passes through the heart fourteen times 

 in one hour ; wdiich is about once every four minutes." 

 Consider what an affair this is, when we come to very large 

 animals. The aorta of a whale is larger in the bore than 

 the main pipe of the water works at London Bridge ; and 

 the water roaring in its passage through that pipe, is in- 

 ferior, in impetus and velocity, to the blood gushing from 

 the whale's heart. Hear Dr. Hunter's account of the dis- 

 section of a whale. " The aorta measured a foot in diame- 

 ter. Ten or fifteen gallons of blood is thrown out of the 

 heart at a stroke, w4th an immense velocity, through a tube 

 of a foot diameter. The whole idea fills the mind v/ith 

 wonder.'"* 



: The account which we have here stated, of the injec- 

 tion of blood into the arteries by the contraction, and of 

 the corresponding reception of it from the veins by the di- 

 lation of the cavities of the heart, and of the circulation 

 being thereby maintained through the blood-vessels of the 

 body, is true, but imperfect. The heart performs this of- 

 fice, but it is in conjunction with another of equal curiosi- 

 ty and importance. It was necessary that the blood should 

 be successively brought into contact, or contiguity, or prox- 

 imity with the air. I do not know that the chemical rea- 

 son, upon which this necessity is founded, has been yet 

 sufficiently explored. It seems to be made to appear, that 

 the atmosphere which we breathe is a mixture of two kinds 

 of air ; one pure and vital, the other, for the purposes of 

 life, effete, foul, and noxious : that wlien we have drawn 

 in our breath, the blood in the lungs imbibes from the air, 

 thus brought in contiguity with it, a portion of its pure in- 

 gredient ; and, at the same time, gives out the effete or 

 corrupt air which it contained, and which is carried away, 

 along with the halitus, every time we respire. At least, 

 by comparing the air which is breathed from the lungs, 

 with the air before it enters the lungs, it is found to have 

 lost some of its pure part, and to have brought away with 

 it an addition of its impure part. Whether these experiments 



' Dr, Hunter's account of the dissection of a whale. Phil. Trans. 



