136 Cincinnati Society of Natural History. 



What the relation of the eighth nerve may be was not determined, 

 but the lighter color of the acusticus fibres serves to distinguish 

 them at their entrance and exit The single strand forming the 

 ninth nerve is quite distinct from the vagus roots, and, after emerg- 

 ing from the ganglion vagi, forms a second small ganglion — glosso- 

 pharyngeal ganglion — whence it passes without branches or 

 anastomosis to the sides of the floor of the mouth near the inferior 

 maxillaries. The ganglion vagi gives origin to two vagus bundles. 



The first of these contains only pure vagus-fibres and is distinctly 

 barred transversely. It passes candad at some distance laterad 

 from the median line, entering the thorax, and passing over the 

 aortic arch, it dips under the vena cava, pulmonary artery and 

 bronchus, giving off numerous branches to the respiratory and 

 circulatory organs, and continues to the abdominal viscera. 



The second of the two vagal strands contains chiefly hypoglossal 

 fibres, and divides half-way to median line, a portion of its fibres 

 passing parallel to the vagus caudad, soon dividing into two 

 strands which anastamose with the sympathetic and form a com- 

 plicated mesh work ; the remainder of the fibres pass under the 

 hyoid cornu and supply the muscles about the head of the trachea 

 and hyoid. 



The roots of the tenth extend obliquely along the lateral protu- 

 berance of the clavae, and consist of a variable number of fibres. 

 Rueckhard speaks of fourteen to fifteen, but figures eleven root- 

 fibres. On both specimens studied we found eleven or twelve such 

 fibres, including the posterior pair, which pass to the accessory and 

 are separated by an interval nearly as long as the root area of the 

 remainder from the next cluster. 



The ninth nerve springs from a point dorsad and anterior to the 

 foremost root of the vagus, and has but two root fibres at its exit. 

 It passes through the jugular foramen. 



The twelfth roots, on the other hand, emerge from a point ventral 

 to the tenth and through a distinct foramen, entering the ganglion 

 of the vagus from a medio-ventral direction. The hypoglossus 

 forms a rather distinct cluster of nerve roots nearer the median line 

 of either side than the following first cervical. Three subordinate 

 groups of fibres may be distinguished, the most anterior containing 

 two, the following from five to seven, and the posterior, from four 

 to five fibres. 



The eighth nerve arises by a strong cylindrical trunk which can 



