Kappers, Teleostean and Selachian Brain. 69 



which, among others, the tractus descendens nervi quinti termi- 

 nates — the nucleus spinalis trigernini, or nucleus Rolandi. This 

 sensory mass extends with diminishing circumference for some 

 distance into the medulla spinalis and in Lophius is the terminal 

 nucleus of sensory spinal roots. 



Over its posterior part are the giant ganglion cells previously 

 examined by Ussow, and Fritsch and after them, among others, 

 by Tagliani, Sargent, Dahlgren, Holmgren, Johnston 

 and Studnicka, who, though not always of the same opinion, 

 describe the course of their neurites and their characteristic 

 vascular supply. Here they are more numerous than farther 

 caudad (cf. Figs. Ixxxiii, Ixxxiv with Ixxxv). 



After this short description of the most important external 

 features of the oblongata, we may proceed to the course of the 

 tracts, the entrance of the nerves and the position of the nuclei. 

 I shall begin with the description of the fibers which connect the 

 more frontal regions with the oblongata, afterward taking up the 

 nerves (cf. Fig. 8, Plate XV). 



As I have already treated of the mesencephalo-cerebellar and 

 thalamo-cerebellar connections, I can begin with the fasciculus 

 longitudinal IS later alls, which in the most caudal parts of the mid- 

 brain appears as a round tract not divided by any septa or only by 

 very small ones (Figs. Ixxxvi, Ixxxvii, Plate VI). In Gadus it 

 continues caudad till near the entrance of the motor trigeminus, 

 where the nucleus of this nerve divides it into two parts (Fig. 

 xci), of which the most lateral part touches the secondary com- 

 munis tract and seems to belong to it. This, however, is not the 

 case. Both frontal and caudal of the trigeminus this bundle 

 again joins the rest of the fasc. lateralis which does not give off 

 any fibers as far as the trigeminus region extends. But farther 

 back it is first divided by several septa into smaller bundles and 

 afterward (see Fig. xciv) decussates entirely and enters the acus- 

 tico-lateralis region. These decussating fibers form there an 

 important part of the fihrce arcuatce dorsales, as also Edinger 

 describes for the reptiles. Accordingly this tract relates the 

 terminal nucleus of the nervus octavus (inclusive of the nervi 

 laterales) with the colliculi, and consequently is to be considered 

 as connecting the static center with a region indirectly connected 

 with the optic system. 



As a second connection of the oblongata with the frontal parts 



