392 NORMAL, HISTOLOGY AND ORGANOGRAPHY. 



traced through the substance of the medulla to their 

 ventral exit. The superficial origin of the twelfth 

 nerve is just anterior to the olive, and the fibers of 

 the tenth nerve may be traced to their superficial 

 origin just dorsal to the olive. In serial cross sec- 



Superficial 



arcuate fibers. 

 Arcuate nucleus. 



Anterior pyramids. 

 Fig. 272. Cross section of the open medulla (composite drawing). 



tions it will be seen that the nuclei of the other cra- 

 nial nerves, from the sixth to the twelfth, lie in the 

 floor of the fourth ventricle. 



The fasciculus solitarius is a bundle of nerve fibers, 

 cut in cross section, and placed just lateral to the 



