58 LABORATORY OUTLINE OF NEUROLOGY 



terminalis, choroid plexus of the third ventricle, anterior 

 medullary velum, and membranous roof of the fourth ventricle 

 (tegmen fossa3 rhomboidese), the last two forming the roof of 

 the ventricle above and below the cerebellum respectively. 



The tegmen fossce rhomboidece includes at its anterior border a 

 thin but nervous plate, the posterior medullary velum, border- 

 ing the attachment to the cerebellum, and further spinalward 

 the convoluted choroid plexus of the fourth ventricle (cf. 

 Section 50). Notice that the fourth ventricle extends a short 

 distance dorsalward into the cerebellum (recessus cerebelli) 



trped.tr 

 c.geamed 



m 



FIG. 12. The lateral surface of the medulla oblongata and midbrain of 

 the sheep. X 1%. br.c.i., brachium of colliculus inferior; br.p., brachium 

 pontis; c.gen.med., corpus geniculatum mediale; coch., nucleus cochlearis; 

 col.inf., colliculus inferior; col.sup., colliculus superior; c.r., corpus resti- 

 forme; f.cun., fasciculus cuneatus; f.lat., fasciculus lateralis; /// to XII, 

 cranial nerves; lem.L, lemniscus lateralis; n.v., nucleus vestibularis ; ped. 

 cer., pedunculus cerebri; pyr., pyramid; trap., corpus trapezoideum ; ir. 

 ped.tr., tractus peduncularis transversus; tr.sp.cb.d., tractus spino-cerebel- 

 laris dorsalis; tr.sp.V., tractus spinalis trigemini; tub.cun., tuberculum 

 cuneatum; V.m., motor root of trigeminus; V.s., sensory root of trigeminus. 



and that it is only in this region that the cerebellum forms the 

 true roof of the ventricle. Note that the roof of the third ven- 

 tricle is also a choroid plexus extending from the pineal body to 

 the interventricular foramen and that a deep fissure, which is 

 outside the brain, extends forward from the region of the ten- 

 torium cerebelli between this plexus and the overlying body of 

 the fornix. In the sheep the medial surface of the hippocam- 

 pus is visible within this fissure (marked "gyms dentatus" in 

 Fig. 10). Locate the attachment of the choroid plexus of the 



