DIRECTIONS FOB LABORATORY WORK 817 



XXII. THE NERVOUS SYSTEM 



(A) THE SPINAL CORD (Medulla spinalis). 



(1) Study l.p. a stained (preferably by the Weigert-Pal technic) 

 transverse section of the spinal cord in the lower cervical region, includ- 

 ing a spinal ganglion. Compare with the upper cervical and thoracic 

 levels. Note the enveloping membranes (spinal meninges) : dura mater, 

 arachnoidea, and the pia mater; and their continuity with the connective 

 tissue envelopes of the spinal nerve. "Sketch (405) a segment through 

 these membranes with the included lymph spaces. Note the greater 

 vascularity of the pia mater spinalis. Note further the compressed oval 

 shape of the lower cervical section, and its division into symmetrical 

 halves by the dorsal longitudinal septum and the ventral longitudinal 

 fissure; also the central canal; the central gray matter arranged in the 

 form of an H with its dorsal, ventral, and lateral horns and their con- 

 stituent cell groups ; the peripheral white substance, divisible into dorsal, 

 lateral, and ventral columns; the gray and white commissures; the sub- 

 stantia gelatinosa centralis, and the gelatinous substance of Rolandi ; the 

 formatio reticularis; the cell column of Clarke; nucleus of Stilling; the 

 connective tissue and neuroglia septa of the white substance; and the 

 dorsal and ventral roots of the spinal nerves. Sketch (406). Describe 

 the structural differences between gray, white, gelatinous, and reticular 

 substances. Compare the lower cervical with the lumbar and sacral sec- 

 tions. Differences? Development of the spinal medulla? Define tract 

 (fasciculus), column (funiculus), and nucleus (of origin and termina- 

 tion) of the spinal cord. Define: conus medullaris, filum terminate, and 

 the cauda equina. Describe the relations to each other of the sensory, 

 motor and association neurons in the spinal cord. 



(2) Study l.p. an injected specimen of the spinal cord of the cat. 

 Note the five longitudinal arterial trunks in the pia mater spinalis : the 

 larger antero-median artery, and the more slender postero-lateral longi- 

 tudinal arterioles (arranged anteriorly and posteriorly to the line of 

 entrance of the posterior nerve roots). Note their further penetration 

 and distribution within the gray and white substances. (Sketch (407). 



Location, structure and function of the septum posticum, the liga- 

 menta denticulata and the subarachnoid spaces? origin of cerebrospinal 

 fluid? Trace the course of the lymph circulation through the central 

 nervous system. 



