CHAP. X.] THE MEDULLA OBLONGATA. 263 



harmonious music if they have been previously duly attuned. But 

 if the instrument be out of order, although the player strike the 

 same notes, and evince equal skill in the movements of his fingers, 

 nothing but the harshest discord will ensue. As, then, sweet 

 melody results from skilful playing on a well- tuned instrument of 

 good construction, so a sound mind, and a brain of good develop- 

 ment and quality, are the necessary conditions of healthy and 

 vigorous mental action. 



Medulla Oblongata. Of the segments of the encephalon above 

 enumerated, the medulla oblongata is that which is more immedi- 

 ately connected with the spinal cord, and through which the brain 

 is brought into communication with the other vital organs and 

 with most of the peripheral parts. It is, therefore, truly f; the link 

 which binds us to life/' In form and general anatomical charac- 

 ters, it very much resembles the spinal cord, with which it is con- 

 tinuous, standing in the same relation to it, as the capital to the 

 shaft of a column. 



In the sense in which we here speak of it, the medulla oblongata 

 is limited above by the mesocephale ; but its constituent fibres ex- 

 tend beyond that segment, and form important connexions with the 

 rest of the brain. It is completely contained within the cranial 

 cavity, its lowest part being just above the level of the plane of 

 the occipital foramen. 



The size of the medulla oblongata is in the direct ratio of that of 

 the nerves which proceed from it. Hence it is very much larger, 

 both absolutely and relatively, in some of the lower animals than in 

 man : in many of them it forms the largest of all the segments 

 of the encephalon, while in man it is much the smallest. 



In the medulla oblongata there is the same symmetry of arrange- 

 ment which we have noticed in the cord. An anterior and poste- 

 rior fissure divide it into two equal and symmetrical portions. The 

 posterior fissure is deep and narrow, and is continuous with that of 

 the cord. The anterior fissure is wider and less deep, and sepa- 

 rated from the same fissure of the cord by certain fibres which cross 

 obliquely from each side in its lower third, decussating each other. 

 These fibres are called the decussating fibres of the anterior pyra- 

 mids, and form, very fitly, an anatomical demarcation between the 

 medulla oblongata and the spinal cord. 



The floor of the anterior fissure is formed by a layer of fibrous 

 matter which is rendered cribriform by the orifices of the numerous 

 blood-vessels which penetrate it. This constitutes a commissure of 

 transverse fibres, similar to that described in the spinal cord. The 



