The Works of William Harvey M.D. / Translated from the Latin with a life of the author

by William Harvey

Neither is it true, as he states,[317] “that the chalazæ, rendered fruitful by the semen of the cock, stand in the place of seed, and that from them the chick is produced.” Nor are the chalazæ, as he will have it,[318] “in colour, substance, and bodily properties so like seed, or bear so strong a resemblance to the embryo in a boiled egg, that we may rightly conceive all the parts designated spermatic to be thence engendered.” I am rather of opinion that the fluid which we have called colliquament, or the thinner portion of the albumen liquefied and concocted, is to be regarded as of the nature of seed, and, if the testimony of our eyes is to be credited, as a substitute for it.

The observation of this venerable old man is therefore unnecessary when he says,[319] “As the whole animal body is made up of two substances very different from one another, and even of opposite natures, viz. hot and cold—among the hot parts being included all those that are full of blood and of a red colour; among the cold all those that are exsanguine and white—these two orders of parts doubtless require a different and yet a like nourishment, if it be true that we are nourished by the same things of which we are made. The spermatic, white, and cold parts, therefore, require white and cold nourishment; the sanguineous, red, and hot parts, again, demand nourishment that is red and hot. And so is the cold white of the egg properly held to nourish the cold and white parts of the chick, and the hot and sanguine yelk regarded as a substitute for the hot and purple blood. In this way do all the animal parts obtain nourishment suitable and convenient for them.” Now we by no means admit that the two fluids or matters of the egg are there as appropriate means of nourishment for different orders of parts. For we have already said that the heart, lungs, kidneys, liver, spleen, muscles, bones, ligaments, &c., &c., were all alike and indiscriminately white and bloodless on their first formation.

Further, on the preceding view of Fabricius it would follow that the heart, lungs, liver, spleen, &c., were not spermatic parts, did not originate from the seed (which he, however, will by no means allow), inasmuch as they too are by and by nourished by the blood and grow out of it; for every part is both formed and nourished by the same means, and nutrition is nothing more than the substitution of a like matter in the room of that which is lost.

Nor would he find less difficulty in answering the question how it happens that when the albumen in the egg is all consumed, the cold and white parts, such as the bones, ligaments, brain, spinal marrow, &c., continue to be nourished and to grow by means of the vitellus? which to these must be nourishment as inappropriate as albumen to the hot, red, and sanguine parts.

Adopting the views commented on, indeed, we should be compelled to admit that the hot and sanguineous parts were the last to be produced: the flesh after the bones; the liver, spleen, and lungs after the ligaments and intestinal canal; and further, that the cold parts of the chick must come together and attain maturity, the white being all the while consumed, and the hot parts be engendered subsequently, when the vitellus fails and ceases from nourishing them; and then it would be certain that all the parts could not take their rise in and be constituted out of the same clear liquid. All such conclusions, however, are refuted by simple ocular inspection.

I add another argument to those already supplied: the eggs of cartilaginous fishes—skates, the dog-fish, &c.,—are of two colours—their yelks are of a good deep colour; nevertheless all the parts of these fishes are white, bloodless, and cold, not even excepting the substance of their liver. On the contrary, I have seen a certain breed of fowls of large size, their feathers black, their flesh well supplied with blood, their liver red; yet were the yelks of the eggs of these fowls—fruitful eggs—of the palest shade of yellow, not deeper than the tint of ripe barley straw.

Fabricius, however, seems in these words[320] to retract all he has but just said: “There is one thing to be particularly 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 imbibed 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,[321] “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 shadow, 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.