THE i KIJKliKLLUM. 



149 



The fibres of the second layer 

 course, for the most part, in an almost 

 vertical plane ; they connect the 

 h-lli'iii with the optic lobes (i^f' 1 

 cereleUi ad corpora bigemina) and with 

 other parts of the brain. 



The fibres of the fourth layer re- 

 ceive numerous long processes from 

 the large cells of Purkinje ; they form 

 a large commissural system, which can 

 be followed ventrally on each side into 

 the pars commi&v.rali*. A part of the 

 fibres ends here in the grey matter, a 

 second portion enters the auditory area 

 and forms a descending auditory root, 

 a third part joins the lateral columns 

 (in the medulla oblonyata}, and more an- 

 teriorly some join the ventral columns. 

 The descending fibres from the cere- 

 bellum, together with the Jibrae arcu- 

 af(/e found in the ventral columns, 

 indicate the presence of a pons Ya- 

 rolit. The fibres of this ventral com- 



Fig. 102. 



Mo 





Ventral view of brain of Bana 

 ctculeiUa. 



He Cerebral hemispheres. 

 Hit Pituitary- bodv- 

 , . L.I it Olfactory lobe* 



missure decussate only on its dorsal L^P origin at ott**arj nerve from 

 surface (Koppen). u L^^ bnd h ^ ispLere ' 



The Yalvnla <rrebeUi contains a few T ,,' Optic tn ^ t . 013 



medullated fibres and the roots of the Ta - c T ^5 '"" 



troe'hlear nerves; these pass from the n^ T 



ii/editHa oUongala into the ralvula /// ocuio-motor nerve. 



rt'/v/y,.-///', C1V)SS ill the median line, and ( r , Trochlear nerve. 



> / Abuueens nerre. 



then proceed forwards as the troch- r - ''-" r/// Tngeminai, facial, and 



j auditors n- 



lear nerves. /A. A", XI Gloiopharj-ngeal, pnenmo- 



. gastric, and atxeseory nerves. 



Ihe pigment in the nan commis&u- 



J. 



rails is arranged in a curved line similar to that found in the me- 

 dulla oblongata, but the line is shortened at either extremity, and 

 does not extend into the 



c. The optic lobes and L'ffi-a <^relri. (Curjji.tra ij^m'ttiata and 

 I'm-* pr<l>r,ti.-ii?ai->x. Reissner ; Lvhv* Optima*, Stieda ; Yierhiigel, 

 Tieilemann; Vierhiigel (Zweihiigel) and Pedun<:u.l.i *:i\-ln, Sc; 

 Mesencephalon, UiixL 



