352 NERVOUS SYSTEM, 



with those of the other side. Their roots may be traced occa- 

 sionally along the middle fissure, almost to the front or under 

 surface of the medulla oblongata. Meckel, whose observations 

 on this subject are highly interesting, is disposed to consider 

 the striae not only as forming the roots of the auditory nerve, 

 but as also related, closely to the trigeminus and to the pneumo- 

 gastric. 



On this surface, also, of the fourth ventricle, or sinus rhom- 

 boideus, but in advance of the preceding striae, there is another, 

 on each side, still larger, which may be distinguished by its al- 

 ways beginning at some distance from the middle fissure. Its 

 direction is transverse, .and it passes just above the anterior ex- 

 tremity of the corpus restiforrne, to run into, or to assist in 

 forming, the root of the auditory nerve. Its existence is much 

 more constant than that of the others. It is considered as an 

 assistant ganglion to the auditory nerve, and in cases of deaf- 

 ness has been deficient. Being principally cineritious, it is 

 called Fasciola Cinerea. 



In tracing the continuation of the structure of the medulla 

 &pinalis, into that of the medulla oblongata, we find that each 

 of the anterior cords of the medulla spinalis, besides crossing 

 with some of its fasciculi at the place mentioned, to wit, at the 

 decussation of Mistiehelli, and continuing their course upwards 

 to form the corpus pyramidale, sends off a larger fasciculus, 

 which ascends behind the eminentia olivaris, and forms the 

 floor of the sinus rhomboideus. There is yet another fascicu- 

 lus of white matter between the others, according to Rosenthal, 

 into which the anterior column of the medulla spinalis is di- 

 vided. He says, that it touches the eminentia olivaris, sur- 

 rounds it, and, after having traversed the annular protube- 

 rance, terminates in the tubercula quadrigemina. 



The posterior cords of the Spinal marrow, being continued 

 into the corpora restiformia, become still more evidently di- 

 vided into two fasciculi, from an increase of their volume, than 

 they were in the vertebral canal. The internal of these fasci- 

 culi stops, by a. pointed termination, near the borders of the 

 sinus rhomboideus, or fourth ventricle of the Brain; while the 

 external is continued on through the annular protuberance to 

 the cerebellum. 



