722 



THE NERVOUS SYSTEM 



follows: fissura longitudinalis anterior, sulcus paraijyraiuidalis, sulcus lateralis vcn- 

 tralis, sulcus postolivaris, sulcus lateralis dorsalis, sulcus paraiuedianus dorsalis. 

 fissura longitudinalis posterior. As will be seen from the previous descrii)tion, 

 however, this summary applies only to the ujjper or i)roximal part of the medulla; 

 in the distal part the fissures become reduced in numl)er owing to some of them 

 becoming confluent with others. Certain of the above-mentioned fissures divide 

 the medulla into columns or areas corresponding, for tlie most part, to the columns 

 of the cord. Thus we have an anterior area between the anterior fissure and the 

 sulcus lateralis ventralis, a lateral area between the last-named fissure and the 

 sulcus lateralis dorsalis, and a pt>sterior area between the sulcus lateralis dorsalis 

 and tlie j)osti'rior fissure. 



The anterior area of the medulla is t)ccui)ied, for the greater part of its extent, 

 by the pyramidal bodies. These are a pair of ])rominences somewhat pyriform 

 in outline, which lie on each side of the anterior median fissure. Tlieir larger ends 

 are directed upwards and abut against the pons where they become slightly con- 

 stricted. Laterally, they are marked off by the sulci parapyramidales. Their 



Fig. 429. — Transverse Section through the Upper Part of the Pons. (Schwalbe.) 



VALVE OF VIElSSEyS LiyOULA 



DESCENDING ROOT OF 

 TRIGEMINAL 



FOI'RTH 

 VENTRICLE 



RAPHE 



FILLET 



SUPERIOR PEDUNCLE 

 OF CEREBELLUM 



POSTERIOR LONGI- 

 TUDINAL BUNDLE 



FORMA TIO 



RETICULARIS 

 TRA CT OF 



FILLET 



TRIG EMI N.\ L 

 NER VE 



BUNDLES OF 

 THE PYRAMIDS 



TRANSVERSE FIBRES OF PONS 



apices are directed downwards and correspond to the decussation of the pyran)ids. 

 The greater number of the fibres pass across at this point and make their way into 

 the lat(iral column of the opposite side of the cord (lateral j>yramidal tract); a small 

 bundle, however, of the outermost fibres of each pyramid runs downwards in the 

 anterior column of the cord of the same side (anterior pyramidal tract). 



The remainder of the anterior column is occupied ])y the funiculus anterior. 

 This is a triangular area of white substance which intervenes betwet'ii the sulcus 

 parapyramidalis and the sulcus lateralis ventralis. Its l)aseis directed downwards, 

 and is continuous with the anterior ground bundle of the anterior cohmm of the 

 cord. Its apex, directed upwards, is wedged in between the olivary and pyramidal 

 bodices. The progressive diminution of the tract when traced upwards is owing to 

 its fibres receding from the surface, being overlapped by the pyramidal body. 



The lateral area of the medulla is narrow below, being formed by the continua- 

 tion of a j)ortion only of the lateral colunm of the cord. Higher up it ex])ands 

 and jiresents: {a) The olivary body and (b) the tubercle of Rolando. The lateral 

 column is a band which passes uj)wards between the sulcus lateralis ventralis and 

 the sulcus lateralis dorsalis. Above, it passes behind the lower })art of the olivary 



