THE DISSECTION OF THE BACK 



93 



The two halves of the medulla spinalis, thus marked off 

 from each other, are to all intents and purposes symmetrical, 

 and they are joined by a more or less broad band or com- 

 missure which intervenes between the anterior fissure and the 

 posterior septum. 



An inspection of the surface of each half of the medulla 

 spinalis brings into view a groove or furrow at some 

 little distance from the postero-median sulcus ; it is called 

 the postero-lateral sulcus. Along the bottom of that groove 

 the fila of the posterior nerve-roots enter the medulla spinalis 

 (O.T. spinal cord) in accurate linear order. There is no 



Fasciculus gracilis 

 Posterior funiculus. /Fasciculus cuneatus 



Entering fila of 



posterior nerve-root 



Formatio reticularis 

 Lateral funiculus 



Central canal 



Root of accessory 



nerve 



Anterior column of 

 grey matter 



Posterior column of 

 grey matter 



Root of accessory 

 nerve 



Fila of anterior 

 nerve-root 



Anterior funiculus 



FIG. 26. Transverse section through the upper part of the 

 Cervical Region of the Medulla Spinalis. 



corresponding furrow on the anterior part of each half of 

 the medulla spinalis in connection with the emergence of 

 the fila of the anterior nerve -roots ; and it should be noted 

 that the anterior root fila emerge over a relatively broad 

 area, which corresponds in its width to the thickness of the 

 subjacent anterior column of grey matter (Fig. 26). 



Grey Matter of the Medulla Spinalis. The grey matter in 

 the interior of the medulla spinalis has the form of a fluted 

 column. When seen in transverse section, it presents the 

 shape of the letter H. In each half of the medulla spinalis 

 there is a mass of grey matter, comma-shaped in section 

 with the concavity directed laterally. The grey columns of 

 opposite sides are connected across the median plane by a 

 transverse band, which is called the grey commissure. The 



