THE MEDULLA SPINALIS OR SPINAL CORD 



757 







S2, S3 and S4 (Bruce). 1 Behind it 

 is not represented in L 5, SI, S 2 nor 

 dorsal rami of the spinal nerves to 

 column. In the cervical and lumbar 

 enlargements, where the anterior 

 column is expanded in a lateral direc- 

 tion, the following additional col- 

 umns are present, viz.: (a) antero- 

 lateral, which consists of two groups, 

 one in C4, C5, C6 the other in C6, 

 C7, CS in the cervical enlargement 

 and of a group from L2 to S2 in 

 the lumbo-sacral enlargement; (6) 

 postero-lateral, in the lower five cer- 

 vical, lower four lumbar, and upper 

 three sacral segments; (c) post-postero- 

 lateral, in the last cervical, first tho- 

 racic, and upper three sacral seg- 

 ments ; and (rf) a central, in the lower 

 four lumbar and upper two sacral 

 segments. These cell groups are evi- 

 dently related to the nerve roots of 

 the brachial and sacral plexuses and 

 supply fibers to the muscles of the 

 arm and leg. Throughout the base 

 of the anterior column are scattered 

 solitary cells, the axons of some of 

 which form crossed commissural 

 fibers, while others constitute the 

 motor fibers of the posterior nerve 

 roots. (See footnote, page 755.) 



Nerve Cells in the Lateral Column. 

 These form a column which is 

 best marked where the lateral gray 

 column is differentiated, viz., in the 

 thoracic region; 2 but it can be traced 

 throughout the entire length of the 

 medulla spinalis in the form of 

 groups of small cells which are situ- 

 ated in the anterior part of the 

 formatio reticularis. In the upper 

 part of the cervical region and lower 

 part of the medulla oblongata as 

 well as in the third and fourth sac- 

 ral segments this column is again 

 differentiated. In the medulla it is 

 known as the lateral nucleus. The 

 cells of this column are fusiform or 

 star-shaped, and of a medium size: 

 the axons of some of them pass into 



1 Topographical Atlas of the Spinal Cord, 1901. 



1 According to Bruce and Pirie (B. M. J., Novem- 

 ber 17, 1906) this column extends from the middle 

 of the eighth cervical segment to the lower part of 

 the second lumbar or the upper part of the third 

 lumbar segment. 



is a dorso-medial column of small cells, which 

 below S4. Its axons probably pass into the 

 supply the dorsal musculature of the spinal 



Lateral 

 columri 



Postero- 

 lateral 



column 



Antero-lateral 

 column 



'Dorso-medial 

 column 



,Antero-medial 

 column 



Dorsal n 



Lateral column 



TH. VI 



Anterior column' 



Postero- 

 lateral 

 column 



Antero-lale 

 column 



f al 



Antero-medial 

 column 



Central column 



S.I 



Postero-lateral 

 column 



Fia. 671. Transverse sections of the medulla spinalis at 

 different levels to show the arrangement of the principal cell 

 columns. 



