THE NERVES OF MOTION AND OF SENSATION, AND THE BRAIN. 261 



Ejoplanation of the Plate. 

 Plate III. 



Fig. 1. A transverse section of the spinal marrow, showing the distinctions of the 

 medullary and cineritious substance. 



Fig. 2. Shows the section with the medullary columns parted at their natural 

 divisions, viz. by insinuating the curette into the cineritious substance, 

 and opening the sulci. 



A. The posterior column. 

 B, B. The lateral columns. 



c. The anterior columns. 



Fig. 3. The same parts still further separated, so as to exhibit the connexion be- 

 tween the posterior columns of the spinal marrow and the motor columns. 

 The letters refer to the same parts as in the last figure. 

 D. The connexion between the posterior and anterior columns. 



Fig. 4. In this view the posterior part of the spinal marrow, that which belongs to 

 the cerebellum, is taken away, leaving those columns only which belong 

 to the cerebrum. As the posterior portions (figg. 2. & 3. a.) enter deeply 

 into the spinal marrow, when they are taken away the remaining columns 

 fall flat on the board, and permit an easy separation. 

 a, a. The cineritious matter which intervenes between the columns belonging 

 to the cerebrum, and those belonging to the cerebellum. 



B. Projecting lines where the posterior columns of the spinal marrow were 



connected with the anterior. (See fig. 3. d.) 

 c, c. The lateral columns, or sensitive columns, after raising the cineritious 



substance. Into these the sensitive roots of the spinal nerves are traced. 

 D, D. A deeper dissection of the cineritious substance exposes here the posterior 



surface of the anterior or motor columns. 



Fig. 5. This figure represents a posterior view of the upper part of the spinal mar- 

 row, and the medulla oblongata. 



A. The two posterior columns of the spinal marrow being dissected up, they 



are here represented diverging towards the cerebellum at g. 



B. The cineritious matter left on the remaining part of the spinal marrow, after 



raising the column (a.). The separation of the columns having been made 

 at the intervening cineritious matter, both surfaces have that matter 

 attached to them — both a and b. 



