Notes on physiology / by Henry Ashby.

  • Henry Ashby
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Notes on physiology / by Henry Ashby. Source: Wellcome Collection.

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    The epithelial cells differ very considerably in shape and size, but they agree in. possessing nuclei and finely granular cell contents. This granular protoplasm has recently been shown to consist of a fine network, the meshes of which contain a hyaline material. The nucleus in like manner consists of a fine network, continuous with the network of the protoplasm, and has one or more nucleoli. Epithelial cells are connected together by a smxall quantity of a homogeneous albuminous substance, termed the inter- cellular cement; it is stained of a dark brown colour by silver nitrate. Epithelium may be divided into the following varieties :— 1. Tesselated or squamous. 4. Glandular. 2. Columnar. 5. Ciliated. 3. Transitional. I. The Tesselated or Squamous variety is arranged either as a (ci) single layer (fig. 7), or (b) in superimposed or stratified layers (fig. 8). {a) A single layer of tesselated epithelium is found lining the pleura, pericardium, peritoneum, arachnoid, arteries, veins, capillaries, lymphatic vessels, acini of the lungs, anterior and posterior aqueous chambers of the eye, and looped tubes of Henle in the kidney. The cells consist of a thin plate with an oval nucleus, but differ considerably in shape ; those lining the serous sacs being polyhedral or nearly cir- cular ; the cells lining the arteries and capillaries being elongated, and the lymphatics having epithe- lium, with an irregular or wavy border. The outline of these cells is readily shown by staining their inter- cellular cement with silver nitrate. (b) The superimposed layers consist of strata of cells, which clothe surfaces specially liable to friction, They cover the true skin, forming the epidermis ; c 3
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