Anatomy of the Brain. 561 



follows the fissures and sulci into the interior parts of the lobes. When 

 a lobe is cut open, the section of these ramifications appear like the 

 branches of a bush, to which is given the name arbor vitce. 



There are no ventricles or cavities in the cerebellum of man, the in- 

 terior of the lobes being composed of white fibrous matter. In the in- 

 terior of each, however, imbedded in the white fibres, is a body of gray 

 vesicular matter, called the corpus dentatum, or the rhomboideum. The 

 white fibrous matter is continuous with the terminations of the fibres 

 which compose three several bundles on each side, which, taken collec- 

 tively, are called the peduncles of the cerebellum ( or crura cerebelli ). 

 The largest of these bundles is from the pons varolii, the fibres of which 

 turn up around the sides of the superior end of the medulla oblongata 

 and take a posterior direction into the lobes of the cerebellum. These 

 are called the middle peduncles. The posterior peduncles are composed 

 of a part of the restiform columns, which detaches itself from the rest 

 and bends backward at right angles to the medulla oblongata, and, at- 

 taching itself to the middle peduncle, accompanies it into the lobes of 

 the cerebellum. The anterior peduncle consists of a bundle of fibres 

 which originates in the cerebellar lobes and proceeds downward along 

 the inner border of the middle peduncle, then forward towards the cor- 

 pora quadrigemina. A part of the fibres seem to connect with the 

 testes, the rest to proceed beneath these bodies in company with the 

 band of Reil, and so to connect with the lateral part of the crura cere- 

 bri. This peduncle thus furnishes the communication between the cere- 

 bellum and cerebrum. 



The connection between the pyramids and the peduncles of the cere- 

 bellum, is a crossed one, the left peduncle being related to the right 

 pyramid, and the right peduncle to the left pyramid. It is doubtful if 

 there is any direct connection between the cerebellar peduncles and the 

 pyramids ; the connection being formed through the cells in the pons 

 the nucleus pontis. 



The valve of vieussens has been mentioned. It is a thin sheet of 

 medullary matter, which forms the separation of the fourth ventricle 

 from the aqueduct of sylvius. By its posterior edge it joins the anterior 

 vermiform process of the cerebellum. Its anterior edge is joined to the 

 rear of the testes. Its lateral edges join the right and left anterior 

 peduncles of the cerebellum, thereby forming a commissure between 

 these peduncles. Its fibres are mostly tranverse, reaching across from 

 one peduncle to the other, but these are also mixed with longitudinal fibres. 



The pineal gland is a small, conical-shaped mass, of soft consistence 

 and reddish color, without any cavity. In its substance, in a little heap 

 at the bottom, are generally found a lot of calcareous granulations. It 

 is single and median, and of varying size in different tribes of animals, 



