Internal secretion and the ductless glands / by Swale Vincent ; with a preface by E. A. Schäfer.

  • Swale Vincent
Date:
1912
Catalogue details

Licence: In copyright

Credit: Internal secretion and the ductless glands / by Swale Vincent ; with a preface by E. A. Schäfer. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    This is the definition of an ordinary or externally secreting gland. The simplest type of a gland consists merely of a layer of epithelial cells placed upon a basement membrane, while beneath the membrane are found blood capillaries and lymph spaces. When such a layer of epithelial cells be- comes invaginated, we have a tubule or saccule possessing a lumen, and forming a simple tubular or saccular gland. Such glands may be coiled, as in the case of the sweat glands, or the secretory portions of the glands may divide, forming branched tubular glands. This branching may occur again and again, until a complicated structure is produced (compound tubular and compound saccular [or racemose] glands). In these glands the terminal portion of the tubes or alveoli are the secretory portions, while the tubes leading to the exterior are the ducts. The gland cell varies in its microscopic appearance, according to its functional condition. In the submaxillary gland and in the pancreas the variations are well known and easily observed—the discharge of the zymogen granules and the growth from the base of the cell of the chromatophilous substance. Similar functional changes may be observed in the epithelium of the intestine (Asher, 10). But it w^as discovered that some of these glands possessed no duct, and they were therefore called ductless glands, or in German more usually Blutgefassdriisen, or Blutdriisen. The latter names are, however, rapidly falhng into disuse, and the terms, ductless gla^nds, or glands with an internal secretion, are replacing them. The assumption was at once made that, since these structures had the characters of glands, they must secrete. But since there was no communication with a free surface, the hypothesis soon arose that in these cases the specific secretion is passed into the blood-stream, and both the process and the product were termed internal secretion. Thus a new conception in regard to the physiological nature of secretion sprang into existence, and the definition of a gland was extended so as to apply to any structure made up of one or more cells of a special epithelial character which form a product—the secretion—which is discharged upon a free epithelial sur- face, such as the skin or mucous membrane, or upon the
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