EPIPHYSIS CEREBRI 



583 



forms are abundant. In young sheep both types of cells are Charac- 

 terized by pigment granules; in aged specimens the pigment is for 

 the most part present in the shape of extracellular clumps. Also in 

 these stages the connective tissue is relatively much more abundant, 



FIG. 500. PHOTOMICROGRAPH OF A PERIPHERAL PORTION OF THE PINEAL BODY 

 OF A 21 CM. SHEEP FETUS, SHOWING SEVERAL CYSTS AND VASCULAR TRABECUL^J, 

 AND AN ENORMOUS NUMBER OF INTRACELLULAR MELANIC GRANULES. X 250. 



and the interneuroglia cells rare. The interne uroglia cells are prob- 

 ably less highly differentiated neuroglia cells, both types originally 

 arising from ependyma. The interneuroglia cells also contain granules 

 and vacuoles of a lipoid nature, perhaps degenerative in significance; 

 no pheochrome granules are demonstrable. Involution begins about 

 the age of 7 years in man and ends about the age of puberty, though 

 regressive histological changes proceed throughout life. Adult corpora 

 pinealia present very variable histologic pictures. 



