Dear Sir.

In Huxley’s Elementary Lessons in Physiology—pp. 33 & 83.—occur the following passages. “All parts of the body which possess blood capillaries—except the brain, the spinal cord, the eyeball &c contain another set of what are termed lymphatic capillaries.”¹

P. 83 “A quantity of fluid equal to that of the blood is probably poured into the blood, daily, from the lymphatic system. This fluid is in great measure the mere overflow of the blood itself—plasma which has exuded from the capillaries into the tissues & which has not been taken up again into the venous current.”²

You were probably aware of both these facts before; I w^d. merely call your attention to them anew, as contributing to endorse your account of the secretion of tears, in the “Expression of the Emotions.”³ It is clear that if the eyeball has no lymphatic overflows for its blood, it will, on slighter occasion, have a greater tendency than other parts of the body to be gorged with blood.

Yours sincerely | Augustine F. Baker.

To Charles Darwin Esq.