108 NATITilAL THEOLOaY. 



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

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

 tion of a whale : " The aorta measured a foot in diameter. 

 Ten or fifteen gallons of blood are thrown out of the heart at 

 a stroke with an immense velocity, through a tube of a foot 

 diameter. The whole idea fills the mind with wonder."* 



The account which we have here stated of the injection 

 of blood into the arteries by the contraction, and of the cor- 

 responding reception of it from the veins by the dilatation 

 of the cavities of the heart, and of the circulation being 

 thereby maintained through the bloodvessels of the body, ib 

 true, but imperfect. The heart performs this office, but it 

 is in conjunction with another of equal curiosity and impor- 

 tance. It was necessary that the blood should be succes- 

 sively brought into contact, or contiguity, or proximity with 

 the air. I do not know that the chemical reason upon 

 which this necessity is founded, has been yet sufficiently ex- 

 plored. It seems to be made apparent, 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 when we have drawer in our breath, the blood 

 in the lungs imbibes from the air thus brought into contigu- 

 ity with it a portion of its pure ingredient, and at the same 

 time gives out the effete or corrupt air Avhich it contained, 

 and which is carried away, along with tie halitus, every 

 time we expire. At least, by comparing the air which is 

 breathed from the lungs with the air which 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 satisfy the question as to the 

 need which the blood stands in of being visited by continual 

 accesses of air, is not for us to inquire into, nor material to 

 our argument; it is sufficient to know, that in the constitu- 

 tion of most animals such a necessity exists, and that the air, 

 by some means or other, must be introduced into a near com- 

 * Hunter's Account of the Dissection of a Whale. Phil. Trans. 



