ORGANS OF THE BODY. 587 



as was formerly supposed, spring from a collection of large cells in the 

 crura cerelelli ad medullam oUongatam, but rather from small cells of the 

 posterior cornu and of the raphe (Deiters). It likewise gives origin to 

 the sensitive portion of the vagus and glossopharyngeus. 



Finally, there still remain in the reticulated grey substance some 

 remote unbroken masses. Towards these the motor portion of the trige- 

 minus advances, a part of whose root constitutes what is known as the 

 " sounding-rod " (Klangstab) of Bergmann. (Stilling, Lenhossek, Deiters.} 

 Further, the facial nerve arises in this neighbourhood. Upon it a sudden 

 bend was discovered by Deiters at a spot corresponding to the emminentia 

 teres in the fourth ventricle. This observer does not regard the nucleus 

 of the last-named nerve as situated near the abducens, as his predecessors 

 believed it to be (Stilling, Clarke, Dean), but rather in the vicinity of 

 the motor nucleus of the trigeminus. Finally, the motor portion of the 

 vagus, discovered by Deiters, takes its origin here also. 



297. 



Turning now to the question : What becomes of the continuation of 

 the three columns of the spinal cord on arrival at the medulla oblongata 1 

 the first point that appears quite evident is that a prolongation of all the 

 nerve fibres of the whole cord into the latter cannot take place. We 

 have to do here rather with a continuation of the fibres in question under 

 a simplified form, and in reduced number, a modification which is most 

 probably effected through the interposition of ganglion cells in a manner 

 similar to that found in the spinal cord. 



The decussating portions of the pyramids were formerly supposed by 

 Schroder van der Kolk to be derived from the anterior columns, but 

 erroneously, for the latter particularly, preserve for a considerable distance 

 into the medulla their original straight course and shape. It is true, 

 that in the lower portion of the latter they become displaced by the 

 extrusion of the decussating fibres of the pyramid; but when these cease 

 to pass across, they assume again their old position, and continue their 

 course augmented by fibres of the hypoglossus, and probably also of the 

 vagus, as longitudinal cords lying at either side of the raphe, and extend- 

 ing far under the pons. 



But the anterior column becomes considerably modified during this 

 course. In the first place, it is traversed by circular fibres springing for 

 the most part from the posterior columns. Again the grey substance 

 commences even very early to make inroads into it. It is characterised 

 here, as in the spinal cord, by the great breadth of its nerve fibres. 



Beneath the pons Varolii, however, fine and also very delicate fibres 

 begin to take the place of the latter. Here we observe an interpolation 

 of ganglion cells in the usual way, so that the apparent continuation of 

 the anterior column under the pons is in reality a second system of fila- 

 ments springing from these, and passing into the cerebrum, and partly 

 also into the cerebellum. 



The lateral columns, which have likewise, though incorrectly, been 

 described as the source from whence the decussating fibres of the pyramids 

 spring (Koelliker, Lenhossek) form the funiculus lateralis of the medulla 

 oblongata, and extend, at least in part, probably as far as the cerebrum. 

 They, too, are affected by the general complication of the medulla oblongata. 



The reader has not yet forgotten the formatio reticularis appearing in 

 the angle of junction of the two cornua of grey matter. A part of this is 



