GRAY MATTER OF THE CORD. 347 



in the third and fourth sacral segments of the cord and in the 

 first three cervical (Cunningham). The first region (from last 

 cervical to second lumbar segment) corresponds in position and 

 extent to the origins of the white rami communicantes ; the second 

 region is at the level of origin of the pelvic splanchnics; and the 

 cell-groups representing this column in the upper cervical seg- 

 ments probably contribute sympathetic fibers to the accessory 

 and phrenic nerves. 



The cells of the intermedio-lateral column are largely of the 

 radicular variety, their slender axones enter into the anterior 

 roots of the spinal nerves. Whether any belong to the strand- 

 variety is not known. They are in contact relation with posterior 

 root-fibers and are also connected with the posterior roots by 

 intervening neurones. Their cerebral connection has not been 

 traced. 



(3) The posterior columna (columna posterior] except in the 

 lower cord, is slender (Fig. 101). It is longer than the anterior 

 columna and reaches the surface in the posterior lateral sulcus, 

 where it receives the posterior roots of the spinal nerves. The 

 posterior columna presents a slight enlargement near its extrem- 

 ity, called the caput columnce, which tapers off to the apex 

 columns. The head is joined to the base by a constricted part, 

 the cervix. The head of the posterior columna is capped by a 

 V-shaped mass of substantia gelatinosa. Spongy substance makes 

 up the remainder of it. The posterior columna separates the 

 posterior from the lateral column of the cord (Figs. 102 and 103). 



The cells of the posterior columna are numerous. In the head 

 of the posterior columna they have smaller bodies than the cells 

 of the columna anterior. They are less definitely grouped and 

 are fusiform in shape throughout the caput columnar, but in the 

 base of the horn, near its medial surface, they have large vesicular 

 bodies and form one of the most definite cell-columns in the 

 spinal cord. The posterior columna neurones are afferent or 

 sensory in function. 



The neurones 0} the head of the posterior columna (Figs. 102 

 and 103) belong largely to the type of Golgi, as the processes of 

 the greater number of them neither enter into the anterior roots 



