1 82 STRONG. [Vol. X. 



its course and, moreover, seems to vary in size pari passu with 

 the variations in size of the fasciculus. It nearly or quite 

 disappears cephalad of the second root of the IX + X. 



The fibres of the fasciculus communis do not appear to be 

 connected directly with nerve cells in the medulla, though, 

 as indicated in Fig. 12, the surrounding cells frequently send 

 their protoplasmic processes into it. As the nerves originating 

 from it are ganglionated, such ganglia are to be considered as 

 its nuclei of origin (" Ursprungskern," Kolliker 34), while the 

 group of cells above described are to be considered possibly 

 as its terminal nucleus ("Endkern," Kolliker 34). It is pos- 

 sible that some fibres of these roots proceed directly to the 

 nucleus without passing into the fasciculus. From Osborn's 

 description this would seem to be the case in Cryptobranchus, 

 for besides the nuclei corresponding probably to the lateral 

 line nuclei and the motor nuclei we have another nucleus 

 (whose character is considered doubtful by Osborn). 



The diminishing size of the fasciculus from the level of the 

 exits of its roots on caudad in the medulla is due to the 

 gradual loss of its fibres as they terminate freely along their 

 route. The peculiar compound character of the fasciculus as 

 described by Osborn is explicable when we consider that the 

 fibres grow into the medulla by means of the various roots 

 and there unite to form the fasciculus. 



It is evident that this tract is composed exclusively or almost 

 exclusively of visceral (splanchnic) fibres innervating the ali- 

 mentary canal and its appendages. Whether, however, it is 

 composed of efferent or afferent fibres or both, is not so clear. 

 It would seem quite certain, however, that many, or most, 

 of the fibres terminating in epithelium are to be regarded 

 as afferent. This is true also of many of the fibres innervating 

 the filtering apparatus. The character of the fibres so richly 

 innervating the curious glands found in the vicinity of the 

 opening of the gill clefts into the pharynx is not so clear. If 

 we assume the existence of secretory fibres, it would seem 

 certain that some of them must be of this character. We have 

 also seen that some of the vaso-motor fibres, including those to 

 the heart, appear to belong to this component. The fact that 



