I have here exhibited strongly indicate the existence of a dense membrane, thrown into folds around the extremities of projecting crystals, just as a loosened tent cloth would be around the point of a cane thrust against it from the inside; and further, the movement of the crystals, when partly dissolved, around the nucleus but confined within the corpuscle as described in the early part of this paper, both tend to show that the cavity of the corpuscle between the nucleus and the membranous envelope is quite unoccupied by solid matter. Third, the perfect freedom with which one side of the cell wall of a red blood globule from the Menobranchus when acted upon by water may float in until it touches the nucleus, and out again to its own place, will, I think, furnish conclusive evidence to any one who sees it as I have done, against the existence of a porous substance which maintains the shape of the blood disk. From these researches, I therefore conclude that the older theory, which asserts the red blood corpuscles of the vertebrata generally are vesicles, each composed of a delicate, colorless, inelastic, porous and perfectly flexible cell wall, inclosing a colored fluid, sometimes crystallizable, cell contents, which is freely soluble in water in all proportions, explains the physical phenomena presented by red blood globules far more satisfactorily than any other hypothesis which has hitherto been advanced; and, moreover, that the usual bi-concave discoid form of the corpuscles in most mammals, as well as the changes of shape which they undergo in fluids of greater or less specific gravity than the liquor sanguinis, becoming crenated in denser, and globular in rarer liquids, are such as to be perfectly explicable by the light of our present knowledge in regard to the laws of the exosmosis and endosmosis of fluids through membranes; the equilibrium of these forces being maintained in normal serum, and one or the other being rendered preponderant if the specific gravity of that fluid is disturbed. EXPLANATION OF PLATE. Red Blood Corpuscles of the Menobranchus, showing Crystallized Cell Contents. No. 1 exhibits two crystals, which, lying transversely, have been broken by the pressure of the cell wall. No. 2, crystals which, instead of breaking, have slipped past one another. No 3, a single large crystal pushing up the nucleus around which the cell wall is folded. No. 5, an unaltered corpuscle. |