362 THE NERVOUS SYSTEM 



the level of the termination of the spinal cord, the level of the origin of the various 

 nerve roots and of their exit from the vertebral canal, and the level of the various seg- 

 ments of the cord with reference to the vertebrae. Note the filum terminale and the 

 cauda equina. From your text-books of anatomy study the meninges and blood- 

 supply of the cord. 



38. The Spinal Cord in Section. Examine the Pal-Weigert sections of the cervical, 

 thoracic, lumbar, and sacral regions, and from them reconstruct a mental picture of the 

 topography of the entire cord. How does it vary in shape and size at the different 

 levels? Identify all the fissures, sulci, septa, funiculi, gray columns, commissures and 

 nerve roots, the reticular formation, the substantia gelatinosa and the caput, cervix, 

 and apex of the posterior gray column. (See pp. 78-84.) 



39. The Microscopic Anatomy of the Spinal Cor d Study all of the histologic 

 preparations of the spinal cord which have been furnished you. (See pp. 85-90.) 

 Study the neuroglia in Golgi preparations. Study the pia mater, septa, blood-vessels, 

 and ependyma in hematoxylin and eosin preparations. Study the nerve-cells in Nissl, 

 Golgi, and silver preparations. Study the myelinated fibers in Weigert preparations 

 and both the myelinated and unmyelinated fibers in the silver preparations. Note 

 the arrangement of each of these histologic elements and be sure that you understand 

 the relations which they bear to each other. 



40. Draw in outline, ventral side down, each of four Pal-Weigert sections taken, 

 respectively, through the cervical, thoracic, lumbar, and sacral regions of the human 

 spinal cord. Make the outlines very accurate in shape and size, with an enlargement 

 of 8 times. Put in the outline of the gray columns, the central canal, and the substantia 

 gelatinosa Rolandi. Put each outline on a separate sheet and do not ink the drawings 

 at present. 



41. Identify the various cell columns in the gray matter and note how they vary 

 in the different levels of the cord (Nissl or counterstained Weigert preparations). 

 (See pp. 89, 90 and Fig. 65.) Indicate these cell groups in their proper places in the 

 four outline sketches of the spinal cord. What becomes of the axons arising from 

 each group of cells? Why are the anterolateral and posterolateral cell groups seen 

 only in the regions associated with the brachial and lumbosacral plexuses? The 

 intermediolateral column only in the thoracic and highest lumbar segments? Why is 

 the gray matter most abundant in the region of the intumescentiae and the white matter 

 most abundant at the upper end of the spinal cord? 



42. What elements are concerned in spinal reflexes? (See pp. 91-94.) 



43. What connections do the fibers of the spinal nerves establish in the spinal cord? 

 What is the origin and the peripheral termination of the somatic efferent fibers, of the 

 visceral efferent fibers, of the somatic afferent fibers, and of the visceral afferent fibers 

 of the spinal nerves? (See pp. 60-63 and Fig. 37.) What are the proprioceptive 

 and exteroceptive fibers, and in what peripheral structures do they end? (See pp. 

 66-72.) 



44. In a pyridin-silver preparation of the cervical spinal cord of a cat note that as 

 the dorsal root enters the cord the unmyelinated fibers run through the lateral division 

 of the root into the dorsolateral fasciculus (Fig. 72). The medial division of the root 

 is formed of myelinated fibers which enter the posterior funiculus. Read about the 

 intramedullay course of these fibers (pp. 95-98)., 



