A treatise on the principles and practice of medicine : designed for the use of practitioners and students of medicine / by Austin Flint.
- Austin Flint I
- Date:
- 1884
Licence: Public Domain Mark
Credit: A treatise on the principles and practice of medicine : designed for the use of practitioners and students of medicine / by Austin Flint. Source: Wellcome Collection.
Provider: This material has been provided by the University of Massachusetts Medical School, Lamar Soutter Library, through the Medical Heritage Library. The original may be consulted at the Lamar Soutter Library at the University of Massachusetts Medical School.
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![significance, but upon the presence in it of living matter or protoplasm (also called bioplasm). Even formless clumps of protoplasm are sometimes called cells. Cells in the animal body are generally, if not always, provided -with nuclei, and are usually devoid of enveloping membranes. Cells multiply by division. The multiplication of cells by endogenous growth and by budding has not been establislied. As the process is usually described, the first step in the proliferation of a cell is the division of its nucleus, and this is followed by division of its body or protoplasm, each segment sui'rounding one of the nuclei. Recent observations show that peculiar alterations in the nucleus, characterized by the appearance of a delicate reticulum, forming the so-called nuclear figures, usher in the process of segmentation. The doctrine of the so-called specialization of cells bears upon pathological new groAvths. Embryo- logical researches have shown that after tlie formation of the three blastoder- mic layers, tlie cells in each produce only certain kinds ol cells and tissues; that, for instance, connective tissue and muscle can spring only from the middle blastodermic layer, and epithelium only from tlie external and internal blastodermic layers (part of the genito-urinary epitlielium possibly excepted). There is much which supports the view that under pathological conditions definite cells can be reproduced only by their kind, that, for example, new epithelial cells are always the oftspring of pre-existing epithelium, and cannot be developed out of connective-tissue cells or white blood-cor])uscles. This view is best established for epithelial and nervous tissue. Connective-tissue cells, however, can be produced apparently by emigrated white blood-corpuscles as well as by pre-existing connective-tissue cells. Regeneration. The subject of the regeneration of tissues after their destruction by wounds and pathological processes, is treated of in extenso in works on surgical patho- logy, and will be considered here only in outline. Some structures are rejjro- duced with great ease, for example, connective tissue and epithelium; others with more difiiculty, as muscular tissue and peripheral nerve-fibres, and, finally, others not at all, such as the central nervous system and the parenchyma of most organs. Fibrillated connective tiss^ie is present in nearly all pathological forma- tions. It may be produced slowly out of the pre-existing connective tissue, or it may be formed out of germinal or granulation-tissue as it is called. This granulation-tissue is composed chiefly of round and spindle-shaped cells with scanty and ill-defined intercellular substance, and with bloodvessels witliout compact walls. The granulation-cells may be derived from emigrated white blood-corpuscles or from proliferated connective-tissue cells. The round cells become spindle-shaped, and finally assume the various forms characteristic of connective-tissue cells; the intercellular substance increases in amount, proba- bly at the expense of the cells, and becomes distinctly fibrillated, and the round and fusiform cells, when they constitute the embryonic walls of the capillaries, change into flat endothelial cells. The fully formed fibrous tissue is not so rich as the granulation-tissue in cells and bloodvessels, some of which tlieretbre are destroyed in the process of development. The newly formed bloodvessels may be, as described, channels simply hollowed out between the gi-anulation-cells which then constitute their walls. Tlie more usual method of their formation, however, seems to be by protoplasmatic offshoots from pre- existing capillaries. As described by Arnold, conical prolongations of proto- plasm project from the capillary walls at certain points and unite with similar otTshoots from other points. These prolongations are at first solid, but subse- quently become hollowed out in their centre, the cavity thus formed communi-](https://iiif.wellcomecollection.org/image/b21198135_0050.jp2/full/800%2C/0/default.jpg)
