. Quarterly journal of experimental physiology and cognate medical sciences. tances the epithelium cells appear quite distinct fromthe colloid, and stain differently from it. There is, in point of fact, a w^ell-marked boundary between the cytoplasm of the cell and the colloid sub-stance, and it is probable that the other appearance is due to the junctionbetween the two being cut obliquely. With regard to the parathyroids. As was stated by Christian! (10)and by Erdheim (11), there is usually in the rat only one parathyroid 342 Kojima on each side, embedded in the upper third of the thyroid subs
. Quarterly journal of experimental physiology and cognate medical sciences. tances the epithelium cells appear quite distinct fromthe colloid, and stain differently from it. There is, in point of fact, a w^ell-marked boundary between the cytoplasm of the cell and the colloid sub-stance, and it is probable that the other appearance is due to the junctionbetween the two being cut obliquely. With regard to the parathyroids. As was stated by Christian! (10)and by Erdheim (11), there is usually in the rat only one parathyroid 342 Kojima on each side, embedded in the upper third of the thyroid substance near thesurface. It can be seen even by the naked eye as a more opaque point inthe substance of the thyroid. It would appear, however, that there areoccasionally aberrant parathyroids in these animals, and one is not perfectlycertain that all parathyroid tissue has been removed even if the two obviousparathyroids are completely excised. Structure of the Normal Parathyroid of the Rat.—The para-thyroid consists of a large number of small cells which are usually com-. FlG. .3.—Section showing adjacent portions of thyroid and parathyroid of male ratfed with an addition ot Ol grm. of sodium iodide per diem to its ordinaryfood during five days. Microphotograph ; magnified 200 diameters. Htema-toxylin-eosin preparation. The thyroid vesicles are distended with colloid. Their lining epitheliumcells are flattened, but rather less so than in the thyroid shown in the thyroid-fed animal (fig. 2). The parathyroid is less com])act than normal (cf. fig. 1),but more so than in the thyroid-fed animal. pactly arranged. Each cell has a clear protoplasm which is comparativelysmall in amount. The cell-nuclei vary in shape, being round, oval, or oblong,but their size is fairly constant (about 5/x). They stain distinctly byhsematoxylin, and contain fine chromatin granules. The cytoplasm isusually faintly stained by eosin. Occasionally there appears a vesicular-like arrangement of the cells,
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