Cytological and histochemical investigations on the pineal organ of the adult frog (Rana esculenta).

Abstract

1. Among the various cellular components of the epiphysis described in adult Rana esculenta, the sensory cells seem to display a spectrum of images in their outer segments after careful fixation. 2. A histochemical analysis has revealed, in addition to an active lipid metabolism and accumulation, the presence of sulfonic acid, glycol, or perhaps acid mucopolysaccharide components in the outer segments of sensory cells and in the pineal lumen. The possible relationships of these materials to sensory or secretory functions of the cells have been considered. 3. Observations by means of silver stains have shown that sensory cells possess the usual neural characteristics of a sensory epithelium, and also a secondary and possibly efferent innervation. This finding has been discussed in relation to the question of secretion. 4. Since the efferent type of innervation is seen on both sensory and parenchymal types of cells, the classification of the latter as of supportive origin has been questioned. 5. Sensory cells have been found in clustered arrangement not only in the epiphyseal lumen, but also in close proximity to the subcommissural organ. These posterior pineal clusters display protuberances extending into the third ventricle. 6. Epiphyseal follicles with a cystein- or cystine-rich protein component in their secretion have been described. The origin and possible functions of such follicles have been discussed especially in relation to the subcommissuralorgan.