CHAP. IL] 



THE BRAIN. 



963 



cells, of striking appearance ; these however seem too few to give 

 origin to at least all the fibres, and there are some reasons for 

 connecting this root with the collection of grey matter called 

 ' locus caeruleus '. Fig. 113, I.e. 



We may probably regard this descending root as belonging to 

 the motor division of the nerve; but it is stated that many of 

 the fibres of this root pass into the sensory root, eventually 

 finding their way, according to some observers, into the ophthalmic 

 branch. 



The sensory root may be similarly traced into a nucleus, the 

 sensory nucleus (Figs. 115 and 112, V. s.) lying lateral to the 

 motor nucleus, and connected with this is the striking tract of 

 fibres, to which already we have so frequently alluded, and which 

 is called the ascending root of the fifth nerve. 



FIG. 113. THROUGH THE FORE PART OF THE PONS. (Sherrington.) 

 (In the line 113, Fig. 108.) 



Py. Pyramidal fibres. F. C. Fibres from the frontal cortex. S.P. Superior Peduncle 

 of the cerebellum. F m. median portion, F I. lateral portion of the Fillet. 

 1. posterior longitudinal bundles. P. C. Q. Posterior corpora quadrigemina. 

 y. Fibres which become detached from the Fillet, and further forward form 

 (the innermost) part of the Pes of the Crus. I. c. locus caeruleus. n. P. Q. 

 nucleus of the posterior corpora quadrigemina ; the outline is made too sharp. 

 IV. bundles of the fourth nerve decussating, IV. n. its nucleus. V. d. descend- 

 ing root of the fifth nerve. Aq. the aqueduct, c. g. the region of central grey 

 matter. 



This ascending root begins as a bundle or bundles of few fibres 

 which may be traced backward as far as at least the level of the 

 second cervical nerve, and is soon conspicuous in transverse sections 

 (Fig. 109 et seq., V. a.) as a semilunar patch of white matter forming 

 a sort of cap on the outside of the swollen caput of the posterior 



