Kingsbury, Oblongata in Fishes. 5 



tract, and the revolution of the wall between the ventral and 

 lateral sulci somewhat from a vertical to a more horizontal posi- 

 tion (Figs. 16-18). 



Nerves. The vagus nerve arises by 4 (or 5) large roots 

 each made up of two or three smaller rootlets. The most 

 caudal root is undoubtedly purely motor and may be recognized 

 some distance caudad of the metatela as an ascending tract. ^ 

 As it passes cephalad it is reinforced several times by fibers from 

 the the ventral horn, especially at its exit where a number of 

 fibers come from the motor vagal nidus (Zwischenzellen of Go- 

 ronowitschj now recognized as a distinct cluster of cells. (Fig, 

 15, ni). The roots cephalad contain both motor and sensory 

 (ganglionated) fibers and all arise in much the same way, the 

 sensory from the fasciculus communis system (lobus vagi) as 

 shown in Fig. 16, the motor from the vagal motor nidus and 

 apparently also from cells of the ventral cornu proper, though 

 they may yet arise from cells of the vagal nidus, the neurite 

 simply bending ventrad first, it having in no case been traced 

 into any cell. The caudal rootlets go ventrad of the spinal Vth 

 tract, the cephalic ones dorsad of it (Fig. 16), while the inter- 

 mediate roots break through it in passing to their exit. It was 

 difficult to determine definitely whether the vagal roots which 

 penetrated the spinal Vth tract drew fibers from it or not. 

 However, those which passed dorsad to it clearly received a 

 small contingent of fine fibers from it. This is important. 

 Strong, from the fact that in Amphibia vagal fibers were closely 

 associated with the spinal (ascending) Vth, considered it proba- 

 ble that the same source for a portion of the fibers of the Xth 

 existed in other Ichthyopsida. It will be seen later that a sim- 

 ilar derivation of a portion of the fibers of the Xth occurs in 

 at least some teleosts. 



Accompanying the vagus is the lateral line nerve which 

 after the former enters the brain continues cephalad some dis- 

 tance and is joined by the IXth which reaches it after piercing 



^In this respect there is a close resemblance between Amia and Necturus 

 (Amphibia) . 



