

SPINAL CORD AND COMMENCEMENT OF MEDULLA OBLONGATA. 181 



tracts situated in the brain was followed by a descending de- 

 generation, which could be traced through the medulla oblongata 

 into the opposite postero-lateral column and the anterior column 

 of the same side. 



You will not so very infrequently have opportunities to 

 trace out the course of the pyramidal columns if, in autopsies on 

 old cases of hemiplegia, you will make sections through the 

 pedunculi, the pons, the medulla oblongata, and the spinal cord. 

 The grayish pyramid of the affected side can generally be clearly 

 distinguished from the normal white one of the sound side. In 

 the spinal cord there will be also a gray, discolored spot in the 

 opposite lateral column. 



In that region of the spinal cord which is occupied by the 

 pyramidal decussation there also appear marked changes in the 

 posterior columns. Gray, ganglionic masses appear first in the 

 inner and then in the outer division of the posterior columns. 

 These are the nuclei funiculi gracilis et funiculi cuneati. These 

 nuclei become blended with the gray matter and materially 

 change its configuration. (In Fig. 107 the first-mentioned of 

 these nuclei can be seen, and both are shown in Fig. 108.) 

 Apparently, the fibres of the posterior columns gradually termi- 

 nate in these nuclei. From the latter, however, masses of fibres 

 are given off, which pass forward through the gray matter and 

 decussate with those of the opposite side (above the pyramidal 

 decussation). The fibres pass later to the fillet, and the upper 

 pyramidal decussation has also been called the decussation of the 

 fillet. 



It is not easy to demonstrate beyond a doubt the existence 

 of the decussation of the lemniscus in the adult organ. All 

 doubt ceases, however, if we examine sections through the me- 

 dulla oblongata of embryos in the seventh month. In this case 

 the decussating medullary pyramidal fibres are not present to 

 blur the clearness of the image, and the fibres of the posterior 

 columns, which alone are medullary, stand out prominently and 

 cannot be mistaken. At first, only the fibres from the nuclei of 



