METEXCEPHALOX 723 



bo.]}', and liere a greyish ])r()inineiice, the grey tubercle of Rolando, conies to the 

 surface. Beyond this the lateral colunni can he toilowed as a narrow hand hehind 

 the olive as far as the transverse groove at the lower border of the jions. The 

 olivary body is an ovoidal prominence from twelve to sixteen millimetres long, 

 which extends upwards as far as the transverse groove at the lower border of the 

 pons. It is separated from the pyraniidal Ijody by the sulcus lateralis ventralis, 

 and marked oflf externally l)y the sulcus postolivaris. Its lower end is crossed l)y 

 the external areiform (il)res. The external arciform fibres emerge from the 

 anterior longitudinal fissure and from the sulcus lateralis ventralis, and arch 

 round the pvramidal and olivary l)odies to join the restiform body of the same 

 side. 



The posterior area of the medulla is occupied in its lower i)art l)y two slender 

 fasciculi, each of whicli cxjjands al)()ve into a tul»erclc. The inner of the two is 

 call(Ml the funiculus gracilis, the outer the funiculus cuneatus. The funiculus 

 gracilis is separated from its fellow of the opposite side by the ])osterior fissure. 

 As it approaches the lower extremity of the fourth ventricle, it swells out into a 

 prominence called the clava. The latter diverges from its fellow of the opposite 

 side, bounding the fourth ventricle. When traced upwards it gradually tapers off 

 into a fine point. To the inner margins of the diverging portions of the clava' a\«' 

 find the oliex and ligulae attached, as already described (page 718). The funiculus 

 cuneatus is placed between the funiculus last described and the lateral area of the 

 nieiluUa. At the level of the clava it swells out into a prominence, the cuneate 

 tubercle. Above this point it disappears from the surface. 



The upper part of the posterior area is occupied by the restiform body. The 

 latter a})})ears at first sight as if it were the continuation upwards of the funiculus 

 cuneatus and of the lateral tract, and this was formerly descrilied to be the case. 

 It is now known, however, that it is formed by the direct cerebellar tract (page 

 742), the external arciform fibres, and the deep or internal arciform fibres. 

 These constituents unite and form a rounded cord which proceeds upwards and 

 then backwards to the cerebellum, forming the inferior peduncle of that body. 

 In its lower part it is embraced by the roots of the auditory nerve. It then passes 

 through a gap or interval between the superior and middle cerebellar peduncles, 

 and ends in the superior vermiform process of the cereVjellum in the nucleus fastigii. 

 It is connected by the arcuate fil)res with the columns of GoU and Burdach, partly 

 by uncrossed and partly by crossed fibres. The uncrossed fibres have been shown 

 to take a larger share in the formation of the restiform body than the crossed fibres 

 CDarkschewitsch and Freud). The crossed fibres all reach the restiform body as 

 arciform fibres ; man}' of these fibres traverse the olivary nucleus but without 

 entering into connection with its nerve-cells (Edinger) ; they also traverse the 

 accessory olives and may pierce the ascending root of the trigeminal nerve; they all 

 decussate at the raphe, and from thence proceed in two grou])S, superficial and 

 deep arciform fibres. The superficial arciform fibres emerge through the 

 anterior fissure of the medulla, some also through the sulcus i)aramedianus ven- 

 tralis, and arch round the pyramidal body and olive to join tlie restiform l)ody. 

 In this part of their course tliey pass between the root-fibres of the ninth, tenth, 

 eleventh, and twelfth nerves. The deep arciform fibres, after crossing in the 

 raphe, traverse the olivary nucleus of the opposite side, and pass thence, through 

 the su])stance of the medulla, into the restiform body. 



The olivary body also sends fibres to the restiform ])ody. Fibres ])assout of the 

 hilum and cross in the raphe; they then traverse the olivary l)ody of the opposite 

 side and join the restiform body. 



As already mentioned, the superficial origins of some of the cranial nerves appear 

 on the surface of the medulla. The sixth, seventh, and eighth nerves come to the sur- 

 face in the transverse groove l)etween the medulla and pons (fig. 411 ). The twelfth 

 nerve appears by a row of filaments in the groove between the olivary and pyra- 

 midal bodies, and in a line with these filaments, opposite the decussation of the 

 pyramids, the upper part of the anterior root of the first cervical nerve comes to 

 the surface. Between the olivary and restiform bodies, the ninth, tenth, and the 

 up])er part of the eleventh nerves make their appearance, and behind the latter the 

 upper filaments of the posterior root of the first cervical nerve reach the surface. 



