Anatomy of the Brain of Bdellostoma Dombeyi 5 



far as they can be traced. jSTot many of tliem branch, but occasionally 

 one is found, after it has turned cephalad, that divides into two 

 branches as in Fig. 32, both branches continuing cephalad. One Golgi 

 slide also showed a few fibers of this nerve which, after division, sent 

 a branch caudad, and one fiber that turned caudad without division. 

 Branching fibers are, however, infrequent. 



The Lateralis Anterior. — This nerve is not a separate and distinct 

 trunk like the lateralis posterior; instead its fibers join the trunks of 

 such nerves as give most convenient passage to their destination. The 

 largest and most conspicuous bundle of lateralis anterior fibers joins 

 the posterior sensory trunk of the trigeminus and runs with it to the 

 skin of the side of the head where these lateralis fibers supply some if 

 not all of the anterior group of lateral line canals. The fibers of this 

 combined trigeminus and lateralis trunk pass over the utricular gan- 

 glion in close juxtaposition to it, and enter the brain surrounded by the 

 fibers of the auditory utricular root (Figs. 15, 26 and 30). So closely 

 are these fibers intertwined and so difficult are they to follow that, 

 judging from hematoxylin sections, it was thought they all entered the 

 acusticus nucleus, and the entire trunk was called lateralis anterior 

 {Acusticus a, Worthington, '05). With Golgi and Cajal sections, how- 

 ever, their true relations are made plain. Figs. 16 and 17 show the 

 greater part of the fibers of this trunk running meso-caudad in the 

 general cutaneous nucleus, while a smaller part turns directly mesad, 

 entering the acusticus nucleus with a bundle of utricular fibers (Fig. 

 16). We have not yet succeeded in disentangling this middle bundle 

 of lateralis anterior fibers from its accompanying utricular fibers inside 

 of the nucleus. This particular bundle cannot be identified in the 

 Golgi sections at our disposal ; the Cajal sections show it to run mesad 

 and slightly caudad to the center of the nucleus, but as the fibers sub- 

 divide they are lost in the maze. 



The anterior bundle of the lateralis anterior is smaller than the 

 posterior bundle just described. It accompanies the anterior sensory 

 trunk of the trigeminus. After this trunk has passed through the 

 cranial capsule on its way to the brain, several small bundles of fibers 

 separate themselves slightly from the others, and instead of entering 

 the general cutaneous nucleus directly, like the rest of the trunk, enter 

 the acusticum at its ventro-cephalic angle (Fig. 18). These bundles 

 run caudad for a short distance through the ventral part of the acus- 

 ticum. and then those of them that belonor to the general cutaneous 



