214 



ANATOMY FOR NURSES. [CHAP. XVIII. 



contraction of muscles can be made to take place. The appli- 

 cation of stimuli to the afferent nerve-fibres ending in a portion 



of the skin will set up 

 changes in the fibres, 

 which changes will be 

 transmitted by them to 

 the gray matter in the 

 posterior root of the 

 spinal cord. These 

 changes or nervous im- 

 pulses, instead of being 

 sent up the cord to the 

 seat of sensation in 

 the brain, and thus 

 giving rise to sensa- 

 tion, are transmitted 

 to the gray matter in 

 the anterior root of 

 the cord, and conveyed 

 thence by the efferent 

 fibres to the muscles, 

 which they cause to 

 contract. This power 

 of transforming an af- 

 ferent into an efferent 

 impulse is termed the 

 reflex power of the 

 spinal cord. 



The sympathetic sys- 

 tem. The sympathetic 

 system consists of a 

 double chain of gan- 

 glia, placed on each 

 side of the spinal 

 column, and united 

 with each other by 



Fio. 124. GENERAL VIEW OF THE SYMPATHETIC longitudinal filaments. 



SYSTEM. 1, 2, 3, cervical ganglia; 4, 1st thoracic T , ,, . f , 



ganglion; 5, 1st lumbar ganglion; 6, 7, sacral gang- ln6 



lion: <, 9, cardiac nerves; 13, branch of pneumo- Ha are Smaller than 



gastric nerve ending in semi-lunar ganglion- 14 ,1 ,1 i j 



epi-astric plexus. ' those in the brain and 



