. The endocrine organs; an introduction to the study of internal secretion . with projections into their cavities, and the lining epi-thelium cells are pronouncedly columnar. In these circumstances thereis usually little or none of the typical colloid material in the vesicles—although the appearance of the cells is suggestive of secretory may be inferred that the secreted material finds in these cases a 14 The Endocrine Organs ready exit from the vesicles, and thus fails to accumulate within them;it is possible that it may also be different in consistence and far as can
. The endocrine organs; an introduction to the study of internal secretion . with projections into their cavities, and the lining epi-thelium cells are pronouncedly columnar. In these circumstances thereis usually little or none of the typical colloid material in the vesicles—although the appearance of the cells is suggestive of secretory may be inferred that the secreted material finds in these cases a 14 The Endocrine Organs ready exit from the vesicles, and thus fails to accumulate within them;it is possible that it may also be different in consistence and far as can be ascertained, these differences of appearance are seen inanimals which are otherwise normal. A glandular structure of this type,but more pronounced, is noticeable in the thyroid in cases of exophthalmicgoitre in man. It is usually there interpreted to indicate the pro-duction of excess of secretion (hyperthyroidism). The epithelium cellsof the vesicles contain fatty granules which are said to increase innumber with age; they are most numerous near the free border. The. FIG. 5. —Section of thyroid, human, injected. (Major.) Highly magnified. The closerelation of the capillaries to the vesicles is shown. colloid is insoluble in alcohol, water, or ether; when coagulated it isreadily stained by eosin, less easily by hasmatoxylin. In fixed sectionsit often appears shrunken away from the epithelium. It is believed tobe formed from granules which are produced within the cells, and whichbecome changed and dissolved on extrusion. Doubtless it contains theactive principles of the secretion, and probably forms a storehouse whencethey can be extracted as required by the organism. A close relationship exists between the size and structure of the thyroidand the state of general nutrition of the animal. The effect of variationsof diet upon the thyroid has been studied in rats by Chalmers Watson (seefigs. GA and 6fi), who has shown that all transitions from an active or super-active orga
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