Page:The Works of William Harvey (part 1 of 2).djvu/551

 wondered at both in the yelk and the white, viz. that neither of them being blood, they are still so near to the nature of blood that they in fact differ but very slightly from it there is but little wanting to constitute either of them blood ; so that little labour and a very slight concoction suffice to effect the change. The veins and arteries distributed to the membranes of both the white and yelk are consequently seen replete with blood at all times ; the white and yelk nevertheless continuing possessed of their own proper nature, though either, so soon as it is im- bibed by the vessels, is changed into blood, so closely do they approach in constitution to this fluid."

But if it be matter of certainty that blood exists no less in the vessels distributed to the albumen than in those sent to the vitellus, and that both of these fluids are so closely allied to blood in their nature, and turn into blood so readily; who, I beseech you, will doubt that the blood, and all the parts which are styled sanguineous, are nourished and increased through the albumen as well as the vitellus?

Our author, however, soon contrives a subterfuge from this conclusion : " Although all this be true," he says, 1 " still must we conceive that the matter which is imbibed by the veins from the yelk and white is only blood in the same sense as the chyle in the mesenteric veins, in which nothing but blood is ever seen; now chyle is but the shadow of blood, and is first perfected in the liver; and in like manner the matter taken up by the veins from the white and yellow is only the shadow of blood/' &c. Be it so ; but hiding under this sha- dow, he does not answer the question, wherefore the blood and blood-like parts should not, for the reasons cited, be equally well nourished by the albumen as by the vitellus ?

Had our author, in like manner, asserted that the hotter parts are rather nourished by that blood which is derived from the vitellus than by that attracted from the albumen, and the colder parts, on the other hand, by that which is derived from the albumen, I should not myself have been much disposed to gainsay him.

There is one consideration in the whole question, however, which is sorely against him; it is this how is the blood

1 Op. cit. p. 55.