224 A MANUAL OF ANATOMY. 



reum, infundibulum (and pituitary gland), the corpora albi- 

 cantia, and the posterior perforated space. The third ven- 

 tricle communicates by means of the foramina of Monro 

 with the lateral ventricles anteriorly, and through the 

 aqueduct of Sylvius with the fourth ventricle posteriorly. 

 The opening into the infundibulum is only a blind one. 



The Pineal Gland. Figs. 33, 39, 46, 47, 54. 



This is a small gland located between the posterior ex- 

 tremities of the optic thalami and resting upon the groove 

 between the anterior pair of the quadrigeminal bodies. It 

 is about as large as a small pea, and is connected to the 

 rest of the brain by a divided stalk, the lower fibres of 

 which connect it with the posterior commissure, the upper 

 fibres, under the name of the peduncles of the pineal gland, 

 running forward along the optic thalami, marking the 

 junction of the superior and internal surfaces, to cross the 

 depression at the floor of the foramen of Monro and join 

 the anterior pillars of the fornix. 



The Corpora Quadrigemina. Figs. 33, 38, 39, 40, 47, 



48, 53, 54- 



These consist of four rounded elevations arranged in 

 pairs, situated on either side of the middle line, between 

 the optic thalami and the cerebellum, and upon the quad- 

 rigeminal lamina which forms the roof of the aqueduct of 

 Sylvius. These pairs are separated from each other by 

 vertical and horizontal intersecting grooves, forming a 

 crucial sulcus. The anterior or superior pair of elevations 

 is called the nates, the posterior pair the testes. 



The quadrigeminal bodies have a narrowing prolongation 

 forward which is called their brachia, or arms. Between 

 these brachia and close to the groove under the pulvinar of 

 the optic thalamus is the internal g-eniculate body, which 



