114 PHYSIOLOGY FOR NURSES 



Injury to the area of the surface matter of the brain 

 governing; these paths causes both motor and sensory 

 paralysis of the opposite side, because all the fibers of 

 both kinds cross before reaching the origin of the spinal 

 nerves which convey these impulses to or from the tis- 

 sues. 



Centers of the Spinal Cord. There are two enlarge- 

 ments of the spinal cord, one situated in the cervical and 

 the other in the lumbar portion. While these ''second- 

 ary brains" can not be located with exactness, there is 

 sufficient evidence to show that the cervical enlargement 

 contains groups of cells or centers which preside over 

 the movements of the upper extremity, accelerate the ac- 

 tion of the heart, cause dilatation of the pupil, and reg- 

 ulate or prescribe the activity of the cervical sympa- 

 thetic system of nerves. There is here also a spinal res- 

 piratory center. 



In the lumbar enlargement are centers controlling the 

 rectum, bladder and the genital organs and the move- 

 ments of the lower limbs. 



THE CRANIAL AND SPINAL NERVES 



The cranial nerves twelve pairs differ from the 

 spinal in being directly attached to some part - of the 

 brain and, usually, in carrying, in each pair, either af- 

 ferent or efferent fibers alone. They are known by num- 

 bers from before backwards and also have synonyms in- 

 dicating their function. The first, or olfactory; second 

 or optic; eighth, or auditory; and ninth, or glosso- 

 pharyngeal, are concerned with smelling, seeing, hear- 

 ing and tasting and are described with the organs of 

 special sense. 



The third, or motor oculi; fourth, or patheticus; and 



