226 



STUDENTS HISTOLOGY 



SPINAL CORD 



The membranes covering the spinal cord will be discussed 

 later; see page 235. 



The spinal cord is composed of gray matter (cellular) and 

 white matter (consisting of nerve-fibers), and serves as a medium 

 of communication between the brain and the peripheral nerve- 

 apparatus. The arrangement of its several parts will be best 

 understood by the study of a transverse section, of which Fig. 

 146 is a diagrammatic representation. 



The gray substance occupies the central portions of the struc- 



FIG. 146. DIAGRAM. CERVICAL SPINAL CORD IN TRANSVERSE SECTION. 



A. Anterior median fissure. 



B. Posterior median fissure. 



C. Anterior or ventral horn. 



D. Posterior or dorsal horn. 



E. Point of emergence of anterior root of spinal nerve. 



F. Posterior root of spinal nerve. 



G. White commissure. 



H. Anterior gray commissure. 

 I. Posterior gray commissure. 

 J. Substantia gelatinosa Rolandi. 



The tracts which are named on the diagram have no definite boundaries histologically. 

 They are physiological areas. 



