RECONSTRUCTION OF HUMAN 853 



nuclear material acljacrnt to thr latrral aii>;k' of the fourth ventricle. This 

 mass of gray matter is the dorsal cochlear nucleus. It gradually increases in 

 thickness and at the same tune extends laterally oxer the acoustic nerve root, 

 conforming to the surlace contour ol the corjjus restilorme which lies unmc- 

 diately subjacent to it. 



The nuclear material gradually extends more and more laterally and 

 ventrally and thickening at its distal extremity it becomes a discrete ventral 

 luicli'ar collection callixl the ventral cochlear nucleus, it occupies the \entro- 

 lateral angle ot the oblongato-pontile junction, it;: most ventral extent lying 

 somewhat m front ol the mid-|)oint on the lateral surlace ol the bram stem. 

 The cochlear nerve root passes through the mesial aspect ol the ventral coch- 

 lear nucleus, splittmg it into two [portions, a lateral mass which overlies the 

 root as an o\al collection ot gray matter, and a mesial portion existing as a Hat 

 lamina ol nuclear tissue aj^jjlied to the mesial aspect ot the entering root. 



In the more caudal portion ol the cochlear complex the ventral and 

 dorsal nuclei arc joined together by a \\ell-delined layer of nuclear material. 

 This la\c'r becomes thinner and thinner as the corpus restitorme moves dor- 

 sally toward its entry into the inlt-rior cerebellar peduncle until a delinitc 

 separation between the two cochlear masses results in the formation of two 

 discrete nuclei, tlu' dorsal and \'entral. A small portion of the dorsal cochlear 

 nucleus persists independent l\ in the angle of the lloor and lateral wall of the 

 lateral \entricle, while the typical o\al-sha])cd mass of nuck'ar material, 

 the ventral cochlear nucleus, continues cephalad and somewhat \entrad as 

 a separated mass of gray matter. The nucleus continues upward to tlu' le\ el 

 ot the delinitne appearanct' of the |)ontile nucleus where it rather abruptly 

 terminates. I he cochlear complex in the human brain stem is much more 

 extensive than that found in the lower forms, the nuclear material being 

 scattered richlx between the libers of the ner\e as that structure aj)|)roaches 

 the brain stem, producing a continuous and dellnite nuclear connection 



