Herrick, Medulla Oblongata of Fishes. 415 



It is evident from the preceding description that the dorsal cornu, 

 spinal V nucleus and substantia gelatinosa are parts of a single 

 structure whose morphological relations are quite simple, the dor- 

 sal cornu being the point of departure for the differentiation of the 

 other two. The termination of a part of the spinal V tract in the 

 funicular nucleus shows, moreover, that the latter nucleus is also 

 intimately related morphologically w^ith the dorsal cornu. 



The relations of the funicular nuclei, however, are not so easily 

 mastered. They are without doubt primarily correlation centers 

 for descending tactile fibers in the spinal root of the trigeminus 

 nerve and for ascending secondary fibers (chiefly tactile in function) 

 in the dorso-lateral fasciculus (Figs. 13 and 14). The latter 

 tract increases notably in size as we pass cephalad and its larger 

 part ends in the funicular nuclei, though a considerable portion 

 extends farther cephalad into the oblongata. Associated with this 

 latter portion are the ascending and descending secondary gusta- 

 tory tracts, a spino-cerebellar tract and the spinal V tract. All of 

 these except the last may properly be regarded morphologically as 

 parts of the dorso-lateral funiculus, whose spinal portion is equiva- 

 lent to the dorsal part of the funiculus proprius lateralis of mam- 

 mals. Accordingly, the funicular nuclei are to be regarded as 

 derivatives of the formatio reticularis, with which the median 

 nucleus is in very close relations, as we saw above. The formatio 

 reticularis in this region contains many small cells and also very 

 large cells which are closely similar to those of the median funic- 

 ular nucleus and the somatic commissural nucleus. These cells 

 are practically equivalent in the three places {cf. Figs. 9, 11, 12, 13 

 and 14). 



The relations of the median funicular nucleus at its caudal end 

 where it begins to appear as a derivative of the underlying formatio 

 reticularis grisea are seen in Fig. 2 (n.fn.m.). As we pass cephalad 

 it rapidly enlarges parallel with the enlargement of the nucleus of 

 the spinal V tract and receives on its lateral border large masses of 

 fibers from the dorso-lateral fasciculus, including both ascending 

 fibers from the spinal cord and descending secondary gustatory 

 fibers from the facial lobe. On the mesial border it receives the 

 greater part of the small dorsal funiculus and dorso-laterally it 

 receives for its entire extent fascicles from the spinal V tract, which 

 break through the intervening nucleus of the spinal V tract, as 

 shown in Figs. 4 and 7. In the boundary between the nucleus 



