Volume 1

Manual of pathological histology / by Cornil and Ranvier.

  • Victor André Cornil
Date:
1882-1886
Catalogue details

Licence: Public Domain Mark

Credit: Manual of pathological histology / by Cornil and Ranvier. Source: Wellcome Collection.

    27/672 page 9
    THE CELL-WALL. embryonic elements is that in which there is an elaboration, within the protoplasm, of substances which did not exist there before ; for example, in the first stage of the formation of fat cells, minute drops of fat may be seen in the protoplasm. In other cases pig- ment granules are found, for example in the cases of cells con- tiguous to red blood-corpuscles which have been extravasated into a tissue. The most important modification which embryonic cells undergo is in the formation of a membrane enclosing the proto- plasm. This membrane is comparable to the secondary mem- brane of vegetable cells where it is composed of cellulose, whilst in animals it is composed of an albuminoid substance : such are fat cells, cartilage cells, &c. In every kind of cell there are strik- ing differences with regard to this membrane. It is still disputed whether it is produced by thickening of the superficial layers of Fig. 6.—Various Phases in the Division of the Nucleolus and Nucleus in Cells from Sarcoma in a Horse. o, nucleus already constricted and having two nucleoli ; b, division more ad- vanced ; c, nucleolus about to undergo division ; d, e, various forms of seg- mentation of the nucleus. Magnified 450 diameters. the protoplasm, or by secretion of the latter. Whichever it may be, it is entirely distinct from the protoplasm, and capable of being isolated from it. This can be well observed in fat cells, cartilage cells, and the epithelial cells of the buccal mucous membrane. To demonstrate this fact in the latter a 40 per cent, solution of potash should be employed. From the moment that a cell is surrounded by a secondary membrane, or that a substance, more often elabo- rated by itself, is formed at its periphery, it is fixed in a permanent form. It then assists in the construction of a tissue, so that it is impossible to study cells without considering the tissues which contain them. Hence we shall study cells in considering the tissues.
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