4 Howard Avers and Julia Worthington 



and 30). Each of these branches may, and generally does, divide again, 

 and sometimes a third time. After the secondary or tertiary division 

 one branch will usually continue in the same general direction as 

 before, the other frequently turns mesad. In many cases it could be 

 followed no further, but in some, after reaching a more mesial part of 

 the nucleus, it turned again and continued in the same direction as its 

 fellow. Figs. 6 and 29 are good illustrations of the branching of these 

 fibers. After each branching the fibers are smaller in diameter, and 

 after the secondary branching they also become beaded; the final 

 product in Golgi sections is a very fine fiber bearing round or oval beads 

 (Fig. 29). These ascending and descending fibers form a large central 

 core, extending almost the entire length of the nucleus, and we have 

 not been able to find any direct connection between these fibers and 

 the cells of the nucleus, i. e., no end plates resting against the body of 

 the cell. When, however, the nucleus is studied in methylene blue and 

 Cajal preparations, it is seen to possess, in addition to cells and fiber:^, 

 an exceedingly fine intercellular network, extending all through it, and 

 composed of the finest fibers thickly beaded with tiny beads. In Cajai 

 sections a few of the finer fibers of the entering acusticus fibers have 

 been found to be connected with this network, and it is probable that 

 this is the destination of all of them. 



The Lateralis Posterior. — This lateral line nerve (Acusticus h, 

 Worthington, '05) enters the medulla on the dorsal surface at the level 

 of the saccularis fibers, entering the acusticus nucleus directly (Figs. 3, 

 8 and 10). It runs cephalo-meso-ventrad until it reaches a point about 

 one-third of the way between the dorsal and ventral surfaces of the 

 nucleus; here it turns latero-cephalad, and runs as a distinct bundle of 

 fibers along the mesial edge of the nucleus (Figs. 5, 6 and 11). As it 

 nears the cephalic end of the nucleus, the fibers separate somewhat 

 (Fig. 32), some of them turning dorsad, some ventrad (Fig. 13), to 

 •distribute themselves in the dorso-cephalo-mesial angle of the nucleus 

 (Figs. 8 and 14). The fibers measure between 1.8 microns and 2.7 

 microns in diameter before they turn cephalad, and are of quite uniform 

 size. Afterwards, during their course cephalad, some of them become 

 irregular in outline (Figs. 13 and 32), the thickened parts being ovoid 

 in shape, and sometimes double the diameter of the fiber, — occasionally 

 the irregularities are almost as sharply defined as the beads of the 

 regular acusticus fibers, Init this appearance is very seldom seen. Most 

 of the fibers, however, maintain approximately the same thickness as 



