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PHYSIOLOGY AND TEMPERANCE. 



conscious of what is going on. These are called sensory 

 nerves. Also, fibres by which impressions travel from the 

 brain and cause muscles to contract or cells to take on 

 increased action. These are called motor nerves. 



12. Spinal Nerves. Thirty-one pairs of nerves are given 

 off by the spinal cord. The openings in the bones of the 

 spine on each side allow them to pass out. Each nerve has 

 two roots, one in front and one behind. The anterior root 

 consists of motor fibres, the posterior of sensory fibres. The 

 two roots unite or are bound together in one sheath. If the 

 anterior root were cut or destroyed by disease, the person 



FIG. 36. Section of Spinal Cord, with roots of spinal nerves. Front view. 



would lose the power of motion in the part supplied by that 

 nerve, that is, that part would be paralyzed. If the posterior 

 root were divided, the power of feeling would be lost. The 

 spinal nerves, after leaving the spinal column, are formed 

 into several groups, where they join together and then branch 

 off to different parts. This collection of nerves is called a 



13. Cranial Nerves. Arising from the base of the 

 brain, the medulla oblongata, and one pair from the upper 

 part of the spinal cord, are the twelve pairs of cranial 

 nerves. They all emerge from the skull, through small 

 channels in the bone. Nearly all of these nerves have their 



