THE NERVOUS SYSTEM 



249 



THE SPINAL 

 CORD . 



Position . 



Length . 

 Thickness 



Coats . 



Structure 



Nerves 



Functions 



Reflex action 



In the spinal canal formed by the vertebral 

 column. 



About eighteen inches. 



Extends from the medulla oblongata to the first 

 lumbar vertebra. 



About one-third of an inch. 



Pia mater delicate, vascular. 



Arachnoid serous, forming a loose bag. 



Dura mate 1 ) tough, fibrous. 



(A layer of fatty tissue lies between the dura 

 mater and the bony canal..) 



Gray matter internal. 



White matter external. 



Anterior fissure. 



\ Posterior fissure deeper and narrower. 

 I Central canal microscopic. 

 f Thirty-one pairs between the vertebrae. 

 j Crowded at the lower extremity of the cord 



J CttUdd <>qili)i<l.. 



Each trunk formed by the union of two roots. 

 T?not* * Anterior motor. 



te 1 Posterior -sensory. 

 Conduction of impressions. 

 A centre for reflex action (gray matter). 

 Sensory fibres cross as they enter the cord. 

 Motor fibres cross in the medulla oblongata. 



f A disturbed condition of sensory fibres 



j Conducted to a nerve centre 



-j Reflected by the nerve centre along motor fibres to theii 



terminations in muscles 

 I Muscular contraction. 



QUESTIONS FOR TOPICAL REVIEW 



1. State fully what is meant by the term vegetative function ......... 207 



2. To what does man owe his position as the head of the animal creation ? 208 



3. What can you state on the subject of special organs for separate 



functions ? ...................................................... 209 



4. Describe, as fully as you can, the structure of the nervous system. 208, 209 



5. Describe the brain, its location, size, shape, and structure ........ 209-211 



6. Describe the brain proper, or cerebrum .......................... 211, 212 



7. Describe the little brain, or cerebellum .......................... 213, 214 



8. Describe the spinal cord ......................................... 214, 215 



9. What are the spinal nerves, and how are they arranged ? .......... 215 



10. What is the character and substance of their tissues ? ............ 215, 216 



11. State and illustrate how the nerve-fibres perform their office ..... 216, 217 



12. Describe the sympathetic system of nerves ...................... 217, 218 



13. State the properties of nervous tissue, and illustrate ............. 218-220 



14. Explain the functions of the nerves ............................... 220 



15. What is meant by transient paralysis of a nerve? Illustrate .... 221, 222 



16. What can you state of the rate of message-motion along a nerve?. . 222 



