CHAPTER XXXV. 

 THE MEDULLA OBLONGATA. 



THE " oblong marrow" is the direct continuation of the spinal 

 marrow, and contains the different items in the construction of 

 the latter, prolonged upwards and mingled with some additional 

 gray masses. The exact relationship of the different parts of the 

 medulla to those of the spinal cord may be best understood if we 

 suppose the latter, when it reaches its upper limit, to be split 

 vertically on its posterior side down to the central canal, and the 

 lateral masses so separated from one another that the central gray 

 part of the spinal cord becomes spread out on the posterior sur- 

 face of the medulla oblongata. The gray matter of the medulla 

 oblongata consists, then, of two portions distinct from each other ; 

 one being the direct continuation of the gray columns of the spinal 

 marrow, and the other being made up of certain gray nodules 

 imbedded here and there among the white strands. These latter, 

 as a rule, subserve special functions, while the continuation of 

 the gray columns of the spinal cord, which are spread out on the 

 floor of the fourth ventricle, contains the nerve-cells that preside 

 over the movements which are most important for the every-day 

 business of life. 



The functions of the medulla may be conveniently divided, in 

 the same manner as those of the cord, into its conducting power 

 and its use as a central nervous organ. 



THE MEDULLA OBLONGATA AS A CONDUCTOR. 



The various columns of the spinal cord are so distributed in 

 the medulla that the anatomy of their course gives some indica- 

 tion of the channels by which impulses are carried through it. 

 But here, as in the spinal cord, we should remember that the 

 white fibres must be regarded as the direct and rapid means of 



