48 Bulletin of Laboratories of Denison University \y°^- ^^ 



great secondary gustatory tracts which leave the lobe for distant 

 centers. The narrow layer of smaller cells adjacent to these 

 may share this function, but their neurites are mostly shorter. 

 The small cells of the other bands of this layer have short neu- 

 rites which terminate for the most part within the lobe and are 

 therefore called intrinsic secondary gustatory neurones. 



Immediately internal to the seventh band of the layer of 

 secondary neurones is Mayser's third layer, the layer of second- 

 ary gustatory fibers, which pass ventrally to constitute the "sec- 

 ondary vagus bundle" of Mayser. These fibers are of small 

 caliber with thin sheaths which take a very pale stain by the 

 Weigert method. 



Internally from the secondary gustatory tract is the motor 

 layer (Mayser's fourth), containing large cells which give rise 

 to motor root fibers of the IX and X nerves. The thick epen- 

 dyma containing large blood vessels is Mayser's fifth layer. 

 Some of its supporting elements are shown in Fig. 6. 



The endings of the peripheral neurones which compose the 

 superficial layer of root fibers of the vagal lobe of the cyprinoids 

 are richly impregnated in many of my Golgi preparations. 

 Those of the deeper layers impregnate with much more diffi- 

 culty. They are seen in Fig. 6. The superficial fibers end by 

 extensive terminal arborizations which ramify widely among the 

 dendrites of the chief secondary gustatory neurones, forming a 

 very dense neuropil in the more superficial parts of the layer of 

 secondary neurones, though some penetrate through the whole 

 thickness of this layer. These endings are shown in Figs. 6 

 and 15 and somewhat imperfectly in Fig. 8. Fig. 6 shows 

 that the slender strands of root fibers pass from the superficial 

 to the deep layers of root fibers throughout the whole extent of 

 the vagal lobe. 



The most caudal fibers of the vagus constitute the descend- 

 ing or spinal root of this nerve, which passes a very short dis- 

 tance caudad to terminate in the grey centers associated with 

 the commissura infima Halleri and funicular nuclei as Cajal 

 ('96, p. 46) describes the endings of the fasciculus solitarius in. 

 the nucleus commissurale of the mouse. 



