Page:Microscopicial researchers - Theodor Schwann - English Translation - 1947.pdf/94

68 the blood-corpuscles to be vesicles. He relied especially upon the manner in which they were acted on by water, whereby they lose their colouring matter, swell, and become round, and under which circumstances he frequently saw the nucleus roll about within the round and very transparent vesicle. The last fact would of itself be sufficiently conclusive. I have not as yet observed this fact; on the contrary, in most instances the nucleus decidedly adheres to the internal surface of the wall of the vesicle, eccentrical as in all cells, though it may probably also sometimes become detached. The fact, however, of the blood-corpuscles becoming swollen and round, renders their cellular nature highly probable. If the envelope (hülle) of the blood-corpuscle were not a flattened vesicle, it might indeed lose its colour and swell in water, but it would retain its flat form, like a sponge when filling with fluid. The circumstance of the nucleus remaining on the wall during the swelling of the blood-corpuscle in water is no accidental appearance; for even in the round blood-corpuscles of a chick, forty-eight hours after the commencement of incubation, when they were not as yet flattened, I found that the nuclei, which were also circular, were not placed in the centre, but lay eccentrical upon the internal surface of the wall. The cellular nature of the blood-corpuscle, and the signification of its separate parts scarcely appear to admit of doubt when regarded in connexion with the whole of this investigation. It is a flattened cell furnished with a cell-nucleus, which is fixed to a spot on the internal surface of the cell-membrane. The size of the cell as compared with the nucleus is not the same in all corpuscles; that of the nucleus is much more constant. The nucleus of some blood- corpuscles of frogs which had swollen in water, also appeared to me in some instances to be hollow. It also loses its flatness in water, but retains its oval figure. I have