CENTRAL RELATIONS OF COMPONENTS. 53 



In Menidia the pre-vagal portion of the fasciculus com- 

 munis contains a portion of the root fibres of the VII and 

 IX nerves, as described in the sections devoted to those 

 nerves, I find no indication of a pre-facial fascicuhis 

 communis. From the communis root of the facialis this 

 tract passes back to the lobus vagi as a compact round 

 bundle lying close to the ventricle. After receiving the 

 sensory IX nerve (Fig. i8) it begins to be surrounded by 

 an area of "ground substance " and almost at once enters 

 the lobus vagi in several strands. 



The lobus vagi crowds the other structures of this 

 region laterally until it occupies nearly the whole of the 

 dorsal part of the oblongata. Upon almost the whole of 

 its lateral face the root fibres of the vagus are received. 

 The lobi vagi are very moderately developed as compared 

 with some other teleosts, e. g:, cyprinoids, and fuse in the 

 median line only at their caudal extremities over the tip 

 of the fourth ventricle. The small size of the lobus vagi 

 may be correlated with the reduction of the terminal bud 

 system in Menidia. 



The motor vagus nucleus (nucleus ambiguus) lies ven- 

 tro-mesally of the lobus, just laterally of the floor of the 

 ventricle and dorsally of the fasciculus longitudinalis dor- 

 salis. (Fig. 17). Caudad of the exit of the motor vagus 

 roots the lobus diminishes in size and the other dorsal 

 structures, z. e., the dorsal comu, nucleus funiculi and 

 spinal V tract, appear in their normal relations. In the 

 spinal cord of these fishes, it should be noted, the dorsal 

 horns are crowded mesally as far as possible, so that they 

 lie up against the dorsal fissure with practically no white 

 column intervening (Fig. 16). 



The following description, though based primarily upon 

 Weigert sections, has been controlled by the examination 

 of a series of sections of the brain of Menidia stained by 

 Nissl's method. The cells of the lobus vagi are minute 

 and densely crowded in a narrow zone along the dorsal 

 and mesal surface of the lobus close under the endyma, 

 with but few cells in the interior of the lobe. On the 



