314 MANUAL OF HISTOLOGY. 



the floor of the fourth ventricle (forming the UnecB transfer see) 

 it receives additions from the lateral gray mass, and emerges 

 from the medulla a little behind the internal root, which, how- 

 ever, it soon joins. 



It is seen that the two roots embrace a column of white 

 matter, which is the inferior peduncle oftJie cerebellum. (See 

 Fig. 140.) In sections just above the edge of the pons, having 

 the oblique direction given in Fig. 132, the region of the sixth 

 and seventh nerves comes into view. The view presented here 

 is different from that in the medulla below. In place of the 

 narrow band of arciform fibres which covered the anterior re- 

 gion of the medulla, nearly the anterior half of this section is 

 composed of transverse, arciform fibres. Imbedded in this 

 structure is a longitudinal bundle of white matter, the contin- 

 uation of the anterior pyramid. The posterior half of the 

 section contains the structures under consideration. 



From a group of multipolar cells at the floor of the fourth 

 ventricle, some distance from the median line, several bands of 

 fibres pass forward and slightly outward, in a somewhat sim- 

 ilar way to the hypoglossal roots lower down. This is the 

 nucleus and root of the abducens nerve. 



Internal to and behind the abducens nucleus, in almost 

 all sections, is seen an oval bundle of what at first sight ap- 

 pears to be longitudinal nerve- 

 fibres. Closer examination, how- 

 ever, shows the fibres to be not 

 straight but looped, and in suc- 

 cessful sections the following ap- 

 pearances are presented. Behind 

 the anterior pyramids and out- 

 side of the abducens root is seen 



Fio. 14 2 .-Diagr.n, of co*n* of fibres in a S r U P f mnltipolar Cells OC- 



KtaKSSS&9Sii cupying the same location as the 



or coil where the fibres change their direction rrrrmr* Pillar! flio Ir-W7av fn fill Tin 

 B, the root proper of the facial nerve. 6 1OU P Called Ult LOW6J 



cleus, lower down. Arising from 



this, and pursuing a course backward and inward, are numer- 

 ous fibres ; these reach the oval bundle before mentioned, enter 

 it, curl upon themselves (see Fig. 142), and emerge at about 

 their point of entrance. The fibres mentioned as appearing 

 longitudinal undoubtedly come from the lower facial nucleus, 

 and curl upon themselves*like the rest. 



