Sorensen, Study of Epiphysis and Roof of Diencephalon. 1 7 



scribes the pineal process in a chick embryo of four days, then 

 the diverticles in a goose embryo of 14 days, and says finally 

 of a chick embryo of 9 days: Here the pineal appears as a large 

 tube with numerous diverticles on all sides. Its structure is 

 the same as that of the brain vesicle from which it takes its ori- 

 gin. A transverse section at this stage shows a cavity on the 

 walls of which are small buds. The tissue of the skull cap- 

 sule lies round about it. In a somewhat older embryo the buds 

 have increased in number and the entire organ is more like the 

 adult pineal gland. 



Mihalcovics (sp-77 ) studied the pineal in chick and rab- 

 bit embryos and gave the following descriptions. 



Situation of the pineal. The pineal gland (glandula v. 

 glans pinealis, conarium v. epiphysis cerebri) in the adult 

 brain lies in the falx cerebri, over the mouth of the aqueduct, 

 and there on one hand is in connection with the connective tis- 

 sue of the pia, and on the other with nervous structures, i. e. 

 with the post-commissure and the pineal stalk. A short projec- 

 tion of the ventricle cavity which he has called the recessus 

 infrapinealis, enters the gland. The above relations in fully de- 

 veloped organs point to some certain connection of the develop- 

 ment with the roof of the third ventricle. 



The pineal process. It has already been mentioned in the 

 developmental relations of the diencephalon that the fun- 

 dament of the pineal gland consists of a forward glove-finger-like 

 projection of the roof-plate, which has been called the processus 

 pinealis. In the chick the pineal projection begins to develop 

 toward the middle of the fourth day and grows in the embry- 

 onic connective tissue over the roof of the diencephalon. In 

 transverse sections the projection is circular and its wall consists 

 of radially situated elliptical cells. Its length is .36 mm., diam- 

 eter .09 mm. and the thickness of its wall is .018 mm. The 

 whole projection is bent obliquely forward, its anterior wall en- 

 tering directly into the middle of the vascular plexus, its poste- 

 rior wall into the cerebral commissure, and the lateral walls in 

 the fundament of the optic lobe region. 



" Epithelfollikel." In the chick the pineal projection re- 



