A histological and histochemical study of the development of the pineal gland in the chick, Gallus domesticus

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Abstract
The pineal gland of the chick is composed of vesicles during much of the incubation period. During incubation, these vesicles increase in size and number and reach maximum development at the 17-day prehatching stage. After day 17, the vesicular tissue decreases and, by 1 day posthatching, only a few vesicles remain. All vesicles have disappeared by 1 month posthatching and the gland has acquired a compact, lobed character. The vesicular cells are secretory in nature and react positively with tests for glycogen, glycoproteins, ribonucleic acid, acid mucopolysaccharides, and neutral lipids. In addition, the specialized apical border of these cells stains intensely for acid lipids. The vesicles contain a secretory product which includes a sulfated mucopolysaccharide component. Based on the intensities of the staining reactions, this secretion is present in greatest amounts during the 15- to 17-day prehatching period. No secretory product could be demonstrated after 1 day posthatching. It appears, therefore, that the development of the vesicular tissue is related to some secretory role and that this role is culminated during the 15- to 17-day prehatching period. After day 17, the decrease and eventual disappearance of the vesicles apparently marks the conclusion of this secretory phase for the gland.

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