THE NERVOUS SYSTEM 1361 



nerves. As seen in transverse section, these funiculi lie near each other 

 as they arise from their nuclei in the grey matter of the lower part of the 

 floor of the fourth ventricle. As the funicuh of the hypoglossal nerve pass 

 forwards and those of the pneumogastric nerve outwards, they diverge from 

 each other, and the substance of the bulb is thereby divided into three seg- 

 ments, which constitute the areas of Flechsig — ventral, lateral, and dorsal. 



The ventral area lies bet^veen the raphe of the bulb and the funiculi of the 

 hypoglossal nerve. Throughout its thickness this area contains the following 

 structures : 



The pvramid and arcuate nucleus. 



The fillet. 



The dorsal or posterior longitudinal bundle. 



The formatio reticularis alba. 



The lateral area Ues between the funicuh of the hypoglossal nerve and 

 those of the pneumogastric nerve. Throughout its thickness this area con- 

 tains the following structures : 



The oUve and inferior oUvary nucleus. 



The nucleus laterahs. 



The nucleus ambiguus (to be afterwards described). 



The formatio reticularis grisea. 



The dorsal area is the region behind the funicuh of the pneumogastric 

 nerve. Throughout its thickness this area contains the following structures: 



The restiform body. • 



The upper part of the cuneate nucleus. 



The descending root of the vestibular nerve | ^ ^ afterwards 



The fasciculus solitanus r \i K^ri 



The spinal root of the fifth cranial nerve J aescriDed. 



The substantia gelatinosa of Rolando. 



Course of Chief Nerve-FunicuU of Spinal Cord through Medulla Oblongata. 



Spinal Cord. Medulla Oblongata. 



Posterior Column. 



Column of Goll. Funiculus Gracilis and Nacleas Gracilis. 



Column of Burdaeh. Funiculus Cuneatus and Nucleus Cuneatus. 



Lateral Column. 

 Crossed Lateral Pyramidal Tract. Inner three - quarters of opposite 



Pyramid. 

 Uncrossed Lateral Pyramidal Tract. Outer one-quarter of Pyramid of 



same side. 

 Dorsal or Direct Spino - cerebellar Lateral Area below Olive, and Resti- 



Tract. form Body. 



Ventral or Indirect Spino-cerebellar \ 



Tract I Lateral Area below Olive, and For- 



Prepyramidal or Rubro-spinal Tract j matio Reticularis. 



Lateral Ground-Bundle J 



Anterior Column. 

 Direct Pyramidal Tract. Outer one - quarter ol Pyramid of 



same side. 

 Ventral Ground-Bundle ^ 



Anterior Marginal Bundle of Lowen- - Dorsal Longitudinal Bundle, 

 thai I 



Development of Medulla Oblongata.— The bulb is developed from 

 the myelencephalon, which is the caudal division of the rhomben- 

 cephalon. 



86 



