Tissue

Collier's New Encyclopedia (1921)

a very fine transparent silk stuff used for veils; white or colored. It was formerly interwoven with gold or silver threads and embossed with figures. Also a very thin kind of paper and cloth interwoven with gold. In entomology, a European geometer moth, Scotosia dubitata. The fore wings have numerous transverse wavy lines; the larva feeds on buckthorn. In histology, a set of cells modified for the performance of a special function; the fabric of which the organs of plants and animals are composed. The structure of tissues, with very few exceptions, is imperceptible to the unassisted eye, and requires the aid of the microscope for its resolution. Tissues which are absent from plants occur in animals; these are called animal tissues, and have a relation to movement or to sensation, as the muscles and nerves. But plants preserve, protect, and sustain themselves, and the corresponding tissues in animals are spoken of as the vegetable tissues; of this kind are epithelium and bone. Tissues always present the same general ge arrangement in the same organism, but are combined combined in different ways in different organisms. In the lower forms of life, whether animal or vegetable, the distinctions between tissues become less and less obvious, and there are organisms so extremely simple that the tissue of their bodies is of a uniform cellular character. Animal Tissues. - The term tissue is used in dealing with (a) the structure of organs, which are composed of various C tissues; and (b) specially of the component parts of organs. In the first and wider sense, the anatomical individual is made up of osseous tissue, or bo bone; muscular tissue tissue, or flesh; adipose tissue, or fat; cartilaginous tissue, or gristle; connective tissue, serving to bind the whole together; and pigmentary tissue, or coloring matter. In dealing with animal tisin the sues strict sense, histological analysis shows them to be much more differentiated and elaborate in structure than those of plants. They may be divided into (a) Epithelium, consisting of nucleated protoplasmic cells, forming continuous masses, either arranged in a single layer, or stratified and forming several superimposed layers. The lining of the tubes and alveoli of secreting and excreting glands and the sensory or terminal parts of the organs of sense consist of epithelium. (b) Connective tissue, a name applied to a variety of tissues de- Cyc. Vol. IX veloped from the same embryonal element, serving more or less as framework or connecting substance for nervous, muscular, glandular, and vascular tissues. In the embryo and in the growing condition one may be changed into the other, and in the adult they gradually shade off one into the other. These tissues are divided into three groups: The epidermal, which covers the exterior of the plant, and usually consists of a single layer of cells; (2) the fibro-vascular, which traverses the body of the plant in the form of bundles, and is characterized by the presence of tubes and vessels, and of long, pointed, prosenchymatous cells the wood fibers; (3) the fundamental tissue, which fills up the rest of the space, and consists principally of parenchyma.