CHAPTER XVI 

 THE PINEAL GLAND 



STRUCTURE OF THE PINEAL 



THE pineal gland or epiphysis cerebri (conarium), which is present in 

 nearly all vertebrates, is in man a small solid organ less than half the size 

 of the pituitary body. It projects from the roof or dorsal wall of the third 

 ventricle (fig. 82, from the cat), and is connected on each side by a short stalk 



:\- ^-" ^' 



FIG. 82. Sagittal section of pineal of cat. Magnified 50 diameters. I am indebted to 

 Dr Kojima for the specimen from which this microphotograph was taken. 



or peduncle to the habenular commissure. The base of the gland has a 

 small infundibular depression (pineal recess) leading from the ventricle 

 just above the entrance of the aqueduct. This recess is the remains of an 

 evagination from the third ventricle, from which the pineal was originally 

 developed. In some reptiles a median eye is developed as a secondary out- 

 growth from this evagination (Baldwin Spencer). The gland is proportion- 

 ately larger in the child than in the adult, and in the female than in the 

 male. Its average weight in man is 0'22 gramme. It lies between the 

 anterior corpora quadrigemina, and is closely invested by pia mater, so 



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