. The plant, an illustration of the organic life of the animal . e measure con-firmed by the researches of Schleiden; and as his* ideas COMPARED WITH THOSE OP ANIMALS. 53 applied by Swann to the tissues of animals, are now ad-mitted by almost all physiologists, the following abridg-ment of them will be acceptable :— When there are the appropriate external conditions, thefirst visible stage of cell-formation consists in the appear-ance of minute granules which trouble the clear gummysolution in the cells, or the interspaces which surroundthem, rendering it turbid and opaque. Some of thesegranul
. The plant, an illustration of the organic life of the animal . e measure con-firmed by the researches of Schleiden; and as his* ideas COMPARED WITH THOSE OP ANIMALS. 53 applied by Swann to the tissues of animals, are now ad-mitted by almost all physiologists, the following abridg-ment of them will be acceptable :— When there are the appropriate external conditions, thefirst visible stage of cell-formation consists in the appear-ance of minute granules which trouble the clear gummysolution in the cells, or the interspaces which surroundthem, rendering it turbid and opaque. Some of thesegranules collect together and form a nucleus around whichother granules (nucleoli) gather, so that they ultimatelyacquire a larger size than the rest. These nucleated agglo-merations, called by Schleiden, cytoblasts, become each anactive centre around which the mucilaginous fluid of theprotoplasm organizes itself. As soon as the cytoblasts arefully grown, a fine transparent vesicle developes on oneside of them. This vesicle first appears as the segment of Fig. Cells of a leek, after Quekett. u, nucleus; i, nucleolus. a sphere, the cytoblast forming its flat side and the wallsof the vesicle its convex surface. The vesicle continues toexpand until at length the cytoblast from which it ori- 5* 54 THE TISSUES OP PLANTS ginated, appears but as a small opaque body, -whicli is eithercentrally located, or attached to one of its walls. Thus, according to Schleiden, the cytoblast or nucleusvisible in the cellule, has originated the cellule itself. Itis seldom, however, that the cytoblast remains visible forany length of time after the cell has been fully formed;generally, it is re-absorbed. The cytoblast is beautifully apparent in the moniliformhairs of Tradcscantia Virginica. The elementary cells which compose the tissues of ani-mals also contain these nuclei or cytoblasts. Fig. 12.
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Keywords: ., bookcentury1800, bookdecade1850, bookidcu3192, booksubjectbiology
