Recent advances in the physiology of motion, the senses, generation, and development. Being a supplement to the second volume of Professor Muller's "Elements of physiology". / by William Baly and William Senhouse Kirkes.
- Date:
- 1848
Licence: Public Domain Mark
Credit: Recent advances in the physiology of motion, the senses, generation, and development. Being a supplement to the second volume of Professor Muller's "Elements of physiology". / by William Baly and William Senhouse Kirkes. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![MULTIPLICATION OF CELLS. Examples of this arc furnished by the ganglion-corpuscles of nerve-sub- stance, and by the ovum. Kolliker, indeed, considers that all ordinary nu- cleated cells should be regarded in the light of secondary or complex cells. 3. From the several details which have just been considered in relation to the development of cells, it would appear that in the cytoblastema there resides some power by which fresh cells can be continually formed out ol an apparently homogeneous fluid. In order that this continual formation of successive crops of cells may be effected, it is essential, however, that constant supplies of new formative fluid should be provided, and it appears to be one of the purposes served by cells, to elaborate this fresh formative material, which, when perfected, is discharged by the solution of the membranous cell-walls. Out of the fresh cytoblastema thus prepared and liberated, the new cells are developed in one or other of the ways above pointed out. And it would seem, as stated by Schwann, that, in the case of animal structures, the continued increase of cells, is in most cases, effected by such fresh development in the free formative fluid. But in several other cases new cells are formed within the cells of a preceding generation, and by these they are surrounded until they have attained a certain degree of development, when they escape, apparently by rupturing the parent cell which then disappears. This endogenous, mode of cell-formation, (or multiplication, as it is commonly termed,) although of common occurrence among vegetable structures, is, however, comparatively rare in animals; the ovum, cartilage, and a few other structures presenting the only known examples of it. It differs from the original development of cells in the circumstance of the new cells being produced more or less directly from some part of a pre-existing cell, which thus acts as a kind of re-productive organ. But it is not improbable that the difference is one more apparent than real, and consists simply in the circumstance of the source whence the new cells originate, being in the one case retained within the parent-cell, and in the other case set free. The best examples of the endogenous mode of cell-multiplication have been already mentioned in describing the changes which ensue in the de- velopment of the ovum.* It was there shewn (in the case of the ovum of Cucullanus elegans) that according to Kolliker’s observation the first step in the process of multiplication consists in the nucleus of the first cell which is formed after the disappearance of the germinal vesicle, becoming constricted in the middle, and subsequently dividing into two equal halves, each of which serves as a separate nucleus, around which a new cell forms; and each new cell in its turn gives rise to two others formed in the same way, and so the process goes on until the whole mass of the ovum is made up of such cells. And Kolliker appears to be of opinion that in most other cases of cell-multiplication the division of the nucleus is the first essential step in the process.] Other cases, however, seem to occur * Sec especially p. GG and p. 71. t Entwickelungs-gescli. der Cephalopoden, p. 150.](https://iiif.wellcomecollection.org/image/b21967660_0136.jp2/full/800%2C/0/default.jpg)
