44 Bulletin of Laboratories of Denison University. [Voi. xiii 



given throughout the remainder of this paper are all camera 

 drawings of single sections, except Fig. 20, which is a compo- 

 site, and the schemata, Figs. 38, 39 and 40. 



First a few words by way of general orientation. The 

 vagal and facial lobes are dorsal structures in the oblongata, but 

 they do «(?/ represent, as commonly taught, the morphological 

 continuation of the dorsal horns of the spinal cord. These are 

 represented in the spinal V tract and its associated substantia 

 gelatinosa Rolandi, their ventro-lateral position in the vagus re- 

 gion of these brains being due to crowding by the more mesi- 

 ally placed gustatory centers. The latter centers, therefore, if 

 morphologically related to anything in the spinal cord, must 

 represent spinal structures lying dorsally of the canalis centralis 

 and beneath the floor of the dorsal fissure. In the oblongata 

 this fissure opens out and its floor becomes greatly extended 

 to form the membranous roof plate (His), or velum medullare 

 posterior, betieatJi which the lobes in question are developed 



(cf. JUDSON HeRRICK, '99, p. 2 1 3). 



Figure 5, taken midway of the vagal and facial lobes of the 

 carp, illustrates how these structures are superposed upon the 

 great longitudinal conduction paths which constitute the chief 

 landmarks of morphological relationship. The spinal V tract, 

 whose substantia gelatinosa at this level is reduced to a mere 

 vestige, lies ventrally of both the sensory and motor vagus 

 roots. Crowded into the space ordinarily occupied by the sub- 

 stantia gelatinosa Rolandi are the great longitudinal secondary 

 gustatory paths, ascending and descending. Mesially of these 

 is the substantia reticularis, shown by Cajal and others to be 

 the continuation of the ventro-lateral funicle of the spinal cord 

 and to be composed of short paths, mostly sensory fibers of the 



Fig. 5. A transverse section taken through the middle of the vagal and facial 

 lobes of an adult carp stained by the method of Weigert-Pal. X i6. 



The layers of the facial lobes and the vagus roots are designated at the 

 right, a. s. X., ascending secondary gustatory tract from the vagal lobe ; com. 

 r. VII, communis (gustatory) root of the facialis entering the facial lobe ; d. s. 

 VII, descending secondary gustatory tract from the facial lobe ; Im., lemniscus 

 (laterales LSngsbilndel, Mayser); jr/. V. spinal root of the trigeminus. 



