794 



THE NERVOUS SYSTEM 



In addition to the fibres having the origin and course described above, and which, 

 constitute the greater mass of the superior cerebellar peduncle, each peduncle is said 

 to contain fibres which (1) arise in the cerebellar cortex of the same and opposite 

 sides of the mid-line, instead of from the dentate nucleus, and which join the peduncle 

 at the side of the dentate nucleus, between it and the restiform body; (2) fibres which 

 do not cross the mid-line in the decussation, but terminate in the red nucleus of the 

 same side; (3) possibly some fibres are not interrupted in the red nucleus, but pass 

 directly into the thalamus; (4) a small proportion of fibres afferent as to the cere- 

 bellum, which arise in the structures of the cerebrum and pass in to the cerebellum ; 

 and (5) the greater part, if not all, of the ascending fibres of the antero-lateral 

 superficial fasciculus (Cowers' tract) of the spinal cord. The latter, instead of 

 entering the cerebellum by way of the restiform body, are deflected in the medulla 



FIG. 589. TRANSPARENCY DRAWING SHOWING THE ORIGIN, COURSE, AND CONNECTIONS OF THE 

 SUPERIOR CEREBELLAR PEDUNCLES (BRACHIA CONJUNCTIVA) IN THE FORMATION OF 

 ' STILLING 's SCISSORS.' 



rn A L AMDS 



- INTERNAL CAPSULE 



UUXTll.E FROM 



i i:i:i> xut-LEuft 



TO TJtALAMI'X 



BUNDLE FKO.V KKll .\TCLEUS 



TO IKTERXAL CAI'XULE 

 - RED NUCLEUK 

 DECUSSA T1ON OF BRACHIA 



CONJUNCTIVA 



. . BRACHIUM CONJUNCTH'U.M 

 (superior petfund' ) 



I. \FER10R PEDUN- 

 - - CLE (resliform bmli/i 



BUXDLE TO CERE- 

 -- BELLA R CORTEX 



DEXTA TE 



NUCLEI'S 



--- MEDULLA OBLONG ATA 



and pass in the lateral tegmentum of the pons to the anterior medullary velum, where 

 they turn backwards to enter the cerebellum in its superior peduncle and pass to its 

 cortex, probably from the outer side of the dentate nucleus (see fig. 605). 



The anatomy of the fourth ventricle. The fourth ventricle is rhomboidal in 

 shape, being considerably widened at the level of the brachia pontis and pointed at 

 each end. Its floor consists of a slight depression in the brain-stem, the fossa rhom- 

 boidea, and corresponds to the floor of the central canal. Its pointed inferior end, 

 the calamus scriptorius, is directly continuous with the central canal, and its narrowed 

 anterior end is continued into the aquseductus cerebri (Sylvii) of the mesencephalon, 

 which is nothing more than a resumption of the tubular form of the canal. The 

 entire cavity of the ventricle is lined with an epithelium which is continuous with 

 the epithelium, or ependyma, of the central canal. 



The roof of the anterior portion of the fourth ventricle is nervous, consisting of a 



