THE NERVOUS SYSTEM. 



287 



Encephalon, f Prose ncephalon, or 



or Brain { f orphr . lin 

 (Continued)l ' bldm ' 



Thalamanceph- 

 alon, or dien- 

 cephalon, 



.Telencephalon, * 



"Optic thai ami, 

 Subthalamic regions, 

 Pituitary and pineal 



bodies, 

 Structures in interpe- 



duncular space, 

 Optic nerve and retina, 

 Hinder part of third 



ventricle. 



Cerebral hemispheres, 

 Olfactory lobes, 

 Lateral ventricles, 

 Foramina of Monro, 

 Anterior portion of third 

 ventricle. 



THE MEDULLA OBLONGATA is the upper expanded portion 

 of the spinal cord, extending between the lower border of the 

 pons and the upper border of the atlas. It is divided by two 

 fissures the anterior and posterior median fissures into two 

 halves, each one of which is subdivided into four columns, from 

 before backward, the following : 



(a) Anterior pyramids, or corpora pyramidalia, are two 

 pyramidal masses of white nervous matter, placed between the 

 anterior median fissure and the olivary body, and continuous with 

 the anterior columns of the cord below; 



(b) Lateral tract and olivary body, are continuous with 

 the lateral columns of the cord below; 



(c) Restiform bodies are continuous below with the poste- 

 rior columns of the cord. They are composed of the fibres of the 

 columns of Goll and Burdach and the direct pyramidal tract. 

 They diverge, the interval between them being the lower portion 

 of the fourth ventricle. 



The structure of the medulla oblongata consists of both 

 white and gray matter, the former arranged into four columns, 

 the latter contained in the interior. 



The gray matter of the medulla is partly arranged into 

 musses and partly continuous with the gray matter of the con I. 

 The posterior horns are called here "the tubercles of Rolando." 

 On the floor of the fourth ventricle the ganglion-cells are ar- 

 ranged into nuclei, from which several of the cranial nerves 

 have their origin. 



THE PONS VAROLII connects the cerebrum above with the 

 cerebellum behind and the medulla oblongata below. On its 

 under surface it presents a groove for the passage of the basilar 

 artery. The upper surface 1 forms a portion of the floor of the 



