. The thyroid gland in health and disease. esicular tissue to vesicles usually met with inyoung thyroids. x 100. cells, contain portions of thymus tissue or of parathyroid small cells may be found scattered through it or arrangedin masses. Some of these are lymphocytes, others, found in morecompact masses, are the foetal rests from which foetaladenomata are said to arise. The Parathyroid Gland is composed of polygonal epithelium-like cells. The cells may be disposed in a retiform manner andseparated by an extremely delicate network of fibres (fig. 4) orthey may be arranged in compa
. The thyroid gland in health and disease. esicular tissue to vesicles usually met with inyoung thyroids. x 100. cells, contain portions of thymus tissue or of parathyroid small cells may be found scattered through it or arrangedin masses. Some of these are lymphocytes, others, found in morecompact masses, are the foetal rests from which foetaladenomata are said to arise. The Parathyroid Gland is composed of polygonal epithelium-like cells. The cells may be disposed in a retiform manner andseparated by an extremely delicate network of fibres (fig. 4) orthey may be arranged in compact masses ; both arrangementsmay be seen in the same glandule. Strands of connective tissue 12 HISTOLOGY AND PHYSIOLOGY from the areolar capsule of the gland, carrying with them theblood-vessels and nerves which supply the epithelium, divide theglandule into irregular lobules. These strands contain plainmuscle and fat cells. The parenchyma cells are of two kinds : the principalcells, which are small with a homogeneous or somewhat granular. Fig. 4.—Section of parathyroid of wild rat showing usual arrangement ofparenchyma cells and capsule of areolar tissue, x 200. protoplasm, and other larger cells containing oxyphil granulesstaining with eosin ; in man the latter only appear after thetenth year (Walsh). Both kinds of cells contain fatty granuleswhich increase in number with age. They probably representdifferent stages of secretory activity of the parencliyma mav be found in the land containino a substance PROCESS OF SECRETION 13 resembling colloid, or more rarely colloid may be fomid lyingbetween the cells. According to Vincent these vesicles in-crease in number with age and after complete removal of thethyroid. Thymus nodules may be found in the parathyroid, just as mayportions of parathyroid be found in the thymus, a fact whichis explained by their similar development. Process of Secretion.—The process of secretion in thehuman subject is difficult to study,
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