The circulation of the blood, through the bodies of men and quadrupeds, and the apparatus by which it is carried on, compofe a fyftem, and teftify a contrivance, perhaps the beft underftood of any part of the animal frame. The lymphatic fyftem, or the nervous fyftem, may be more fubtile and intricate; nay, it is poffible that in their ftructure they be even more artificial than the fanguiferous; but we do not know fo much about them.

The utility of the circulation of the blood, I affume as an acknowledged point. One grand purpofe is plainly anfwered by it; the diftributing to every part, every extremity, every nook and corner, of the body, the nourifhment which is received into it by one aperture. What enters at the mouth, finds its way to the fingers' ends. A more difficult mechanical problem could hardly I think be propofed, than to difcover a method of conftantly repairing the wafte, and of fupplying an acceffion of fubftance to every part, of a complicated machine at the fame time.

This fyftem prefents itfelf under two views: firft, the difpofition of the blood veffels, i. e. the laying of the pipes; and, fecondly, the conftrùction of the engine at the centre, viz. the heart, for driving the blood through them.