Hand-book of physiology / by W. Morrant Baker and Vincent Dormer Harris.

  • William Morrant Baker
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Hand-book of physiology / by W. Morrant Baker and Vincent Dormer Harris. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

    49/914 page 27
    CH. in.] VARIETIES OF CELLS. 2*] (a.) From their shape, cells are called spherical or spheroidal, which, is the typical shape of the free cell; this may be altered to polyhedral when the pressure on the cells in all directions is nearly the same ; of this the primitive segmentation-cells afford an example. The discoid form is seen in blood-corpuscles, and the scale-like form in superficial epithelial cells. Some cells have a jagged outline and are then called prickle-cells. Cells of cylindrical, conical, or prismatic form occur in various places in the body. Such cells may taper off at one or both ends into fine processes, in the former case being caudate, in the latter fusiform. They may be greatly elongated so as to become fibres. Cells with hair-like processes, or cilia, projecting from their free surfaces, are a special variety. The cilia vary greatly in size, and may even exceed in length the cell itself. Finally, cells may be branched or stellate, with long outstanding processes. (b.) From their situation cells may be called free, as in the blood, or combined, when connected together or with other elements to form organs and tissues. (c.) From their contents cells are called, when containing fat for example, fat-cells ; when containing pigment, pigment-cells, &c. (d.) From their function cells are called secreting, protective, sensitive, contractile, and the like. (e.) From their origin cells are called epiblastic and meso- blastic and hypjoblastic. Modes of connection.—Cells are connected together to form tissues in various ways. (1.) By means of a cementing intercellular substance. This is probably always present as a transparent, colourless, viscid, albu- minous substance, even between the closely apposed cells of epithelium, while in the case of cartilage it forms the main bulk of the tissue, and the cells only appear as imbedded in, not as cemented together by, the intercellular substance. This intercellular substance may be either homogeneous or fibrillated. In many cases {e.g., the 'cornea) it can be shown to contain a number of irregular branched cavities, which communicate with each other, and in which branched cells lie : through these branching spaces nutritive fluids - can find their way into the very remotest parts of a non-vascular tissue. As a special variety of intercellular substance must be men- tioned the basement membrane (membrana propria) which is found at the base of the epithelial cells in most mucous membranes, and especially as an investing tunic of gland follicles which determines their shape, and which may persist as a hyaline saccule after the gland-cells have all been discharged.
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