Page:The Harveian oration, 1875 (IA b22314611).pdf/30

 the household divinity which nourishes, cherishes, quickens the whole body—the foundation of life, the source of all action.

I stop for a moment to remark that, at the time Harvey wrote, nearly a century and a half was yet to elapse ere the chemical discoveries of Priestley superseded poetry by fact, and transferred to the laboratory of the lungs those life-giving changes which Harvey and his contemporaries thought they saw carried on in the workshop of the heart.

The consideration that inspired this poetic outburst of Harvey’s was this—that the quantity of blood, circling through the body in some given short space of time, is far too large to be supplied by the ingesta, or used up in the process of nutrition. Harvey had gauged the left ventricle of the heart, and found it to hold upwards of two ounces of blood; and reducing his estimate of the quantity sent out at each contraction and prevented from returning by the action of the valves, to the absurdly low figure of one drachm (and all the world, he says, allows that with every systole something is projected), he calculates thus: —In half an hour, the heart beats more than 2000 times, and so sends forth in that short space of time more blood