MEDULLA OBLONGATA AND TEGMENTUM OE THE PONS. 399 



Flechsig and Hosel have proved that the median fillet ends in the nuclei of the 

 posterior columns of the cord. They consider the whole bundle direct from the 

 cerebrum as the cortical fillet. It has already been stated that the cerebral tract, 

 here concerned, ends in the ventral thalamic nucleus, and that there the median, or 

 superior, fillet arises. 



So we have lemniscal fibers to all the sensory bulbar nuclei. The lem- 

 niscus contains, therefore, the secondary sensory fibers, and conducts them up- 

 ward to the mesencephalon and the thalamus. Monakow succeeded in demon- 

 strating the experimental proof of this at the same time that the author 

 called attention to it from comparative anatomy. In experimental pro- 

 duction of degeneration the fillet may, indeed, be separated into its various 

 bundles for the different nerves, trigeminus, aeusticus, etc. 



In the same horizontal level as the fillet, dorsal to the pons, one finds, 

 near the median line, another bundle of thick fibers. It comes from the 

 pyramidal region of the crura. It has already been shown how it separates 

 there, and, passing around the entire crus internally, reaches the median 

 side of the fillet. Spitzka, from comparative anatomy, has made it seem 

 probable that this bundle contains the central paths of the motor cranial 

 nerves. As a matter of fact, one can convince himself that from it fibers 

 ascend continually toward the raphe, and can see on the dorsal end of the 

 raphe fibers crossing over the median line to the nuclei, at least to that of the 

 hypoglossus. 



We arrive now gradually in the region of the pons, where the roof of 

 the metencephalon is no longer formed by the cerebellum, but rather by 

 the veliim meduUare anticum. Here the fourth ventricle begins to narrow 

 down into the aquteductus Sylvii. 



The single component parts of the tegmentum in this level appear dis- 

 tinctly in the accompanying, not schematic, transverse section through the 

 uppermost portion of the pons in a fetus of nine months. In the crus at this 

 time there is but a small bundle of medullated fibers. In the tegmentum, 

 however, the lemniscus, the brachium (superior cerebellar peduncle), the 

 posterior longitudinal fasciculus, and many fibers of the substantia reticu- 

 laris are completely developed. The brachium passes directly into the 

 velum medullare anticum, on which rests the anterior part of the lingula. 

 Below, above the lemniscus, can be seen the hindmost fibers of the brachia 

 crossing. 



The descending trigeminal root lies on either side of the aqueduct as a 

 thin bundle of fibers. Median to it, underneath the floor of the fourth ven- 

 tricle or the anterior portion of the sinus rhomboidalis, must be imagined 

 the cells of the locus cceruleus, which were not distinct in the preparation 

 copied. The substantia reticularis here consists principally of longitudinal 

 fibers, which can be followed upward only as high as the anterior quadri- 



