Page:Microscopicial researchers - Theodor Schwann - English Translation - 1947.pdf/20

AUTHOR'S PREFACE. these observations of Dumortier, in as much as they regard the tissue consisting of cells as the yolk and not the liver. (Bulletin de l’Acad. royale de Bruxelles, tom. v, No. 5.)

Other instances of the resemblance in form between different animal tissues and those of vegetables had already been repeatedly pointed out. Thus it was frequently said, in reference to thickly-crowded animal cells, or even mere globules, that they presented an appearance resembling vegetable cellular-tissue; and Valentin (Nov. Act. N. C. xvui, P. 1, 96), after describing the nucleus of the epidermal cells, states that it reminded him of the nucleus which occurs in the vegetable kingdom, in the cells of the epidermis, the pistil, &c. Nothing, however, resulted from such comparisons, because they were mere similarities in figure, between structures which present the greatest variety of form.

Schleiden instituted researches into the mode of development of vegetable cells, which illustrated the process most excellently. This admirable work appeared subsequently in the second part of Müller’s Archiv for 1838. He found, that in the formation of vegetable cells, small, sharply-defined granules are first generated in a granulous substance, and around them the cell nuclei (cytoblasts) are formed, which appear like granulous coagulations around the granules. The cytoblasts grow for a certain time, and then a minute transparent vesicle rises upon them, the young cell, so that, in the first instance, it is placed upon the cytoblast, like a watch-glass upon a watch. It then becomes expanded by growth. Schleiden communicated the results of his investigations to me, previous to their publication in October, 1837. The resemblance in form, which the chorda dorsalis, to which J. Müller had already drawn attention, and the branchial cartilage of the tadpole present to vegetable cells, had previously struck me, but nothing resulted from it. The discoveries of Schleiden, however, led to more extend researches in another direction.