STRUCTURE OF THE MEDULLA OBLONG ATA. 



portion of grey matter is continuous below with part of the anterior horn, and the 

 roots of the hypoglossal and sixth nerve appear to correspond generally with the anterior 

 roots of the spinal nerves. In traversing the substance of the bulb they mark off an 

 anterior area, wedge-shaped in transverse section, which is placed between them and 

 the anterior median fissure. This area is on the surface marked by the prominence 

 known as the pyramid or anterior pyramid, which corresponds in position (but only 

 to a small extent iu the fibres of which it is composed) with the anterior column of 

 the spinal cord. The remainder of the transverse section of the bulb, after the 

 posterior and anterior areas are deducted, lies between the line of nerve-root bundles 

 of the hypoglossus and sixth on the one side, and that of the successive bundles of the 

 spinal accessory, vagus, glosso-pharyngeal, and seventh on the other. This is termed 

 by Flechsig the lateral area, and on the surface it is marked by a continuation 

 of part of the lateral column of the cord, and by the prominence of the lower olive 

 already alluded to. 



"We may now proceed to describe in detail the several parts which appear upon 

 the surface of the bulb in the three regions thus marked off by the two sets of 

 nerve-roots, commencing with the posterior area. t 



Posterior area. It will be remembered that in the upper region of the 

 spinal cord a small portion of the whole posterior column is marked off from the rest 

 by a well-developed pia-matral septum, and is indicated on the surface by a distinct 



Fig. 35. POSTERIOR AND LATERAL VIEW OF THE 



MEDULLA OIJLONGATA, FOURTH VENTRICLE AND 

 5IESENCEPHALON. (E.A.S.) NATURAL SIZE. 



The cerebellum and inferior medullary velum, 

 and the right half of the superior medullary 

 velum, have been cut away, so as to expose the 

 fourth ventricle. 



p.n., line of the posterior roots of the spinal 

 nerves ; p.m.f., posterior median fissure ; 

 f.g., tuniculus gracilis ; cl., its clava; f.c., 

 funiculus cuneatus ; f.R-, funiculus of 

 Rolando; r.l>., restiform body; e.g., lower end 

 of the fourth ventricle (calamus scriptorius) ; I, 

 section of the lingula or tsenia ; part of the 

 choroid plexus is seen beneath it ; l.r., lateral 

 recess of the ventricle ; sir, strice acusticse ; i.f., 

 inferior (posterior) fovea ; s.f., superior (anterior) 

 fovea ; between it and the median sulcus is the 

 funiculus teres ; cbl, cut surface of the left 

 cerebellar hemisphere ; n.d., central grey matter 

 (nucleus dentatus) seen as a wavy line ; s.m.v., 

 superior (anterior) medullary velum ; Ing, lin- 

 gula ; s. c.p. , superior cerebellar peduncle cut 

 longitudinally ; cr, combined section of the 

 three cerebellar peduncles (the limits of each are 

 not marked) ; c.q.s., c.q.i., corpora quadrigemina 

 (superior and inferior) ; fr, frsenulum veil ; /, 

 fibres of the fillet, seen on the surface of the teg- 

 mentum ; c, crusta ; l.g. , lateral groove ; c g. i. , 

 corpus geniculatum internum ; th, posterior part 

 of thalamus ; p, pineal body. The Roman num- 

 bers indicate the corresponding cranial nerves. 



longitudinal prominence bounded later- 

 ally by a shallow groove. The portion 

 thus marked off is the postero-mesial 



column (tract of Goll), and the prominence, which is continued up into the medulla 

 oblongata, becomes there still better marked, arid is known as the funiculus gracilis 

 (fig. 35, f.(f). This, as it is traced upwards, especially as the fourth ventricle is 

 approached, broadens out into an expansion termed the clava (cl), and as the ventricle 

 opens out the clavas of opposite sides diverge and form the lateral boundary to the 



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