18 Dr. Foville on the dnatomy of the Brain. 



dialing transversely from the former into the latter. It ap- 

 pears also that a greater number of the fibres going to the 

 roots of the spinal nerves proceed directly from the axis itself. 

 This distribution is more evident with respect to the posterior 

 than to the anterior roots. 



Without attempting to describe the lateral columns of the 

 spinal marrow, I must not omit to mention a remarkable dif- 

 ference between the lateral parts of these columns and the 

 anterior and posterior portions. If a portion of the spinal 

 marrow be cut out transversely, freed from its membranes, 

 and left to macerate in plain water for a few hours, the lateral 

 parts of each half will assume, in consequence of the swelling 

 of their fibrous fasciculi, an appearance something like that 

 of a large nerve, whilst the anterior and posterior parts ad- 

 joining these lateral columns are uniformly swelled without 

 presenting any such appearance. Let us now see how the 

 axes of the superficial columns of the spinal marrow are con- 

 nected with the parts developed at their upper extremity, 

 that is to say, in the medulla oblongata. 



The anterior part of the axis, in other words, the anterior 

 part of the commissure, appears to go almost entirely into the 

 decussation of the anterior pyramids, and into the pyra- 

 mids themselves. A very fine commissure between the pyra- 

 mids seems to be a continuation of the anterior commissure 

 which exists throughout the whole length of the spinal mar- 

 row. 



The posterior commissure ascending along the medulla 

 oblongata comes very near to the surface, and when examined 

 between the two lateral portions of the medulla, it seems to 

 constitute a very delicate bond of union between the two sides 

 of the calamus scriptorius. This union seems to be established 

 by means of two slight fibrous columns, which are prolonga- 

 tions of the posterior commissure of the spinal marrow. 



If these statements are correct, we see that when the pro- 

 longations of the commissures or naked surfaces of the axis 

 of the spinal marrow are examined in the medulla oblongata, 

 instead of being very near each other on the median line, they 

 are separated by all the interval existing between the anterior 

 and posterior surfaces of the medulla oblongata. But so 

 slight are the remains of the commissures when examined in 

 the medulla oblongata, that it is very easy to overlook them. 

 When the two halves of the medulla oblongata are separated, 

 and this separation is easily produced by introducing and 

 gently pressing a probe between the two anterior pyramids 

 or the two halves of the calamus scriptorius, they present to 

 our view fibres going from before backwards, and so dis- 

 posed, that those on the right side correspond to the intervals 



