135° A MANUAL OF ANATOMY 



measures about | inch. Superiorly it is separated from the pons 

 Varolii by a deep transverse groove, and interiorly the anterior 

 superficial arcuate fibres arch over its lower part. 



At the lower border of the pons Varolii, external to the upper end 

 of the olive, the facial and auditory nerves make their appearance. 

 The facial nerve is internal in position, and is in line with the funiculi 

 of the glosso-pharyngeal nerve. The auditory nerve appears 

 external to the facial nerve, and between the two is the small pars 

 intermedia of Wrisberg. 



Dorsal or Posterior Area of the Medulla Oblongata. — ^This super- 

 ficial area is limited in front by the dorso-lateral sulcus, containing 

 the funiculi of the glosso-pharyngeal, pneumogastric, and bulbar 

 part of the spinal accessory nerves. Posteriorly its lower half 

 extends as far as the dorsal median fissure, and its upper half 

 extends only as far as the lateral boundary of the lower or bulbar 

 half of the floor of the fourth ventricle. Inasmuch as this area 

 pertains to both the closed and open parts of the bulb it will be 

 considered in two sections — Slower and upper. 



Lower Portion of Posterior Area. — This portion, as stated, is 

 limited behind by the dorsal median fissure, and it is in direct 

 continuity with the dorsal column of the spinal cord of the same 

 side, which is composed of the columns of Goll and of Burdach. It 

 presents three longitudinal eminences — ^namely, the funiculus 

 gracilis, funiculis cuneatus, and funiculus of Rolando. 



The funiculus gracilis is a prolongation of Goll's column of the 

 spinal cord, and lies close to the dorsal median fissure. The funi- 

 culus cuneatus is a prolongation of Burdach's column of the cord, 

 and lies external to the funiculus gracilis, from which it is separated 

 by an upward continuation of the dorsal intermediate or para- 

 median furrow of the cord. 



At the level of the calamus scriptorius each of these two funiculi 

 becomes enlarged and terminates in a prominence or bulb. The 

 enlargement formed by the funiculus gracilis is called the clava, 

 and that formed by the funiculus cuneatus is termed the cuneate 

 tubercle. The two clavse, right and left, lie on either side of the 

 calamus scriptorius, and, as the bulb opens out dorsally at this 

 level to form the lower or bulbar half of the floor of the fourth 

 ventricle, each clava is displaced laterally. An angular interval 

 now separates the two clavae, and the prolongation of the central 

 canal of the spinal cord through the lower or closed part of the bulb 

 opens into the fourth ventricle in the angle between the two clavse. 



The funiculus gracilis, with its clava, and the funiculus cuneatus, 

 with its cuneate tubercle, are to a large extent produced by the 

 collections of grey matter which they contain — ^namely, the nucleus 

 funiculi graciHs and nucleus funiculi cuncati. 



The funiculus of Rolando is situated on the outer side of the 

 funiculus cuneatus, between it and the funiculi of the bulbar part 

 of the spinal accessory nerve. It is produced by the substantia 

 gelatinosa of Rolando, which comes close to the surface in the 



