30th Nov. 1653.
LETTER VI
To John Daniel Horst, principal Physician of Hesse-Darmstadt
Excellent Sir,—I am much pleased to find, that in spite of the long time that has passed, and the distance that separates us, you have not yet lost me from your memory, and I could wish that it lay in my power to answer all your inquiries. But, indeed, my age does not permit me to have this pleasure, for I am not only far stricken in years, but am afflicted with more and more indifferent health. With regard to the opinions of Riolanus, and his decision as to the circulation of the blood, it is very obvious that he makes vast throes in the production of vast trifles; nor do I see that he has as yet satisfied a single individual with his figments. Slegel wrote well and modestly, and, had the fates allowed, would undoubtedly have answered his arguments and reproaches also. But Slegel as I learn, and grieve to learn, died some months ago. As to what you ask of me, in reference to the so-called lacteal veins and thoracic ducts, I reply, that it requires good eyes, and a mind free from other anxieties, to come to any definite conclusion in regard to these extremely minute vessels; to me, however, as I have just said, neither of these requisites is given. About two years ago, when asked my opinion on the same subject, I replied at length, and to the effect that it was not sufficiently determined whether it was chyle or one of the thicker constituents of milk, destined speedily to pass into fat, which flowed in these white vessels; and further that the vessels themselves are wanting in several animals, namely, birds and fishes, though it seems most probable that these creatures are nourished upon the same principles as quadrupeds; nor can any sufficient reason be rendered why in the embryo all nutriment, carried by the umbilical vein, should pass through the liver, but that this should not happen when the fœtus is freed from the prison of the womb, and made independent. Besides, the thoracic duct itself, and the orifice by which it communicates with the subclavian vein, appear too small and narrow to suffice for the transmission of all the supplies required by the body. And I have asked myself farther, why such numbers of blood-vessels, arteries, and veins should be sent to the intestines if there were nothing to be brought back from thence? especially as these are mere membraneous parts, and on this account require a smaller supply of blood.
These and other observations of the same tenor I have already made,—not as being obstinately wedded to my own opinion, but that I might find out what could reasonably be urged to the contrary by the advocates of the new views. I am ready to award the highest praise to Pecquet and others for their singular industry in searching out the truth; nor do I doubt but that many things still lie hidden in Democritus’s well that are destined to be drawn up into the light by the indefatigable diligence of coming ages. So much do I say at this time, which, I trust, with your known kindness, you will take in good part. Farewell, learned friend; live happily, and hold me always
Yours, most affectionately,
William Harvey.
London, 1st February, 1654-5.
LETTER VII
To the distinguished and learned John Dan. Horst, principal Physician at the Court of Hesse-Darmstadt
Most excellent Sir,—Advanced age, which unfits us for the investigation of novel subtleties, and the mind which inclines to repose after the fatigues of lengthened labours, prevent me from mixing myself up with the investigation of these new and difficult questions: so far am I from courting the office of umpire in this dispute! I was anxious to do you a pleasure lately, when, in reply to your request, I sent you the substance of what I had formerly written to a Parisian physician as my ideas on the lacteal veins and thoracic ducts.[59] Not, indeed, that I was certain of the opinion then delivered, but that I might place these objections such as they were before those who fancy that when they have made a certain progress in discovery all is revealed by them.