29. CHAPTER I. THE COMPOSITION AND GENUINE ESSENCE OF THE BLOOD.
LEEUWENHOEK has observed, that blood drawn from his own hand was composed of red globules floating in a crystalline humor not unlike water, but that he was in doubt whether all blood was of the same nature. He says, that upon a close examination of the globules, after separating one from the other, and even dividing some of them, they presented the appearance of being very slightly colored. Milk he found in like manner to consist of globules floating in a limpid humor, but these were transparent. (Philosophical Transactions, n. 102, p. 23.) He also clearly discerned, as he says, that every globule was compounded of six smaller ones, which were as flexile and soft as the larger. That in proportion as the larger were stretched out or elongated, the smaller assumed the same lengthened figure, till they became like threads. He also relates that he had subjected the larger globules to violent motion, when they burst in pieces, and displayed the smaller globules. Also that the globules of milk were of different dimensions, but that those of the blood were of only one dimension. (Lectiones Cutlerianoe, v., p. 84, 86.) He saw that the globules were flexible and pliant in proportion as the blood was healthy, and in passing through the small capillary arteries and veins, changed to an oblong figure (Phil. Trans., n. 117, p. 380), three times as long as broad: also that they passed by and into one another, and by reason of their softness could be moulded into various shapes, but when at liberty immediately recovered their former globular condition. Where many globules came together, and lost their heat, they appeared as a uniform matter in which no parts were distinguishable. (Lect. Cutl., p. cit.) When the author was ill, the globules of the blood he drew from himself appeared to he harder and firmer; but when he was in a good state of health, they were better connected with each other, being softer and more fluid: whence he infers, that death may sometimes proceed from the hardness of these globules. (Phil. Trans., n. 117, p. 380, 381.) When he examined blood possessing much crystalline liquor, and placed in one of his tubes, and carried it into the open air at a time when there was a pretty strong wind, he observed that the globules were agitated, like the air itself, by concussions and mutual motions; and he observed moreover another kind of motion, in that each globule gyrated round its own axis. (Ibid., n. 106, p. 129, 130.) He likewise observed that the transparent liquor in which the red globules of the blood swim, itself consisted of small globules, which were fewer before evaporation than after. In the same liquor he also distinguished certain bodies of a quadrangular figure, which he considered to be saline particles. (Ibid., n. 117, p. 380.) But the globules of the blood, he says, are specifically heavier than the crystalline liquor, for the moment they escape from the veins, they by little and little subside toward the bottom; and being made up of soft, fluid corpuscules, and lying one upon another, they unite together, and by their close conjunction, the blood that is under the surface alters its color, and becomes dark red, or blackish. The red globules, he says, are 25,000 times smaller than a grain of sand. (Ibid., n. 106, p. 122.) He observed that in a tadpole the particles of blood were flat and oval, and that sometimes, by reason of the tenuity of an artery, they were made to assume a tapering figure, and were so minute, that a hundred thousand myriad of them could not equal in bulk a large grain of sand. (Epist. 65, Arcana Naturae Detecta, p. 161, 162.)
