THE SYMPATHETIC NERVOUS SYSTEM 287 



the large ganglia which are situated there, as well as 

 the large nerves near by, and make such a profound 

 impression upon the heart that death may take place 

 at once. Blows upon the neck or abdomen are always 

 dangerous. 



SUMMARY 



1. The sympathetic nervous system consists of collec- 



tions of nerve cells called ganglia, and of both 

 sensory and motor nerves which follow the course 

 of the arteries. 



2. The cells of the spinal cord send impulses to the 



ganglia, and they in turn distribute them to the 

 arteries and glands and to the organs of the chest 

 and abdomen. 



3. The ganglia send orders only in a reflex way accord- 



ing to impressions received from their sensory 

 nerves. 



4. The ganglia control the contraction and dilatation of 



the arteries, the peristalsis of the intestine, the secre- 

 tion of glands, and the growth of the cells of the 

 body. 



5. The ordinary sensory impulses conducted by the sym- 



pathetic nerves produce no feeling. 



6. The heart is controlled mainly by a set of small ganglia 



within its own walls. 



7. The sympathetic system produces slow and gentle 



movements in contrast with the quick and active 

 movements made by the spinal cord. 



8. The brain has no direct control over the ganglia. 



9. Blows upon the neck or abdomen may injure the sym- 



pathetic nerves so as to cause death. 



