612 



PHYSIOLOGY. 



crescent is swollen. The posterior is more slender and reaches to 

 the surface of the cord. Each cornu possesses a swelling (head) and 

 a somewhat restricted portion (cervix). 



The head of the posterior cornu is remarkable in that it is 

 capped with a layer of neuroglia to which has been given the name 

 of gelatinous substance of Rolando. It is nearly amorphous, and, in 

 section, gives an appearance very similar to the small letter u. The 

 substantia contains a few neuroglia cells, with some fusiform nerve- 

 cells along its margin. 



R. post. 



Fig. 23G. Two Nerve-pairs at Their Origin in the Spinal Cord- 

 Anterior and Posterior Roots. (MoRAT.) 



As regards the upper pair the figure shows the relation of the roots with 

 the gray axis. In the lower pair is seen the emergence of the anterior roots 

 at the surface of cord. 



In the inferior cervical and superior thoracic region the most 

 lateral portion of the anterior cornu is shaped in a special fashion so 

 as to constitute a particular prolongation. This is known as the 

 lateral cornu, or intermedio-lateral column. The cells of this column 

 are arranged in groups of from eight to twelve bipolar cells whose 

 long axes are vertical or more or less oblique. It is believed that 

 these give origin to those fine medullated fibers which form, the 

 splanchnic efferent fibers. 



On examination of sections it is seen that the anterior cornua 

 do not reach to the surface of the cord. Hence that portion of the 



