116 PHYSIOLOGY ANt> TEMPERANCE. 



THE ELEVENTH PAIR are called the accessory, because they 

 join the tenth pair. They also supply the organs of voice. 



THE TWELFTH PAIE are called the hypo-glossal, or regulators 

 of the tongue. 



14. The Sympathetic System. In this system we have 

 the nerves of organic life. It is a double chain of ganglia, 

 with nerves connecting them. They are situated on each side 

 of the backbone, from the head to the lower extremity of the 

 spine, w r ith extensions into the chest and abdomen. They 

 consist of soft, gray matter, and supply the organs on which 

 life depends, as the stomach, lungs, heart, etc. They control 

 the blood-vessels, and have frequent connections with the 

 cranial and spinal nerves. Blushing is a sympathetic act, 

 allowing the blood-vessels of the face to enlarge and fill with 

 blood. Fear, on the other hand, blanches the face, by the 

 sympathetic nerves contracting the blood-vessels and driving 

 out the blood. 



This intimate relationship of all the nerves of the body, 

 keeping every part in free communication and in close 

 sympathy with every other part, explains the designation, 

 "sympathetic system." By the sympathetic system, the 

 brain has free intercourse with every part of the human 

 frame, and by this link exercises control over all the im- 

 portant functions and vital operations of the body. 



15. Growth and Development of the Brain. As we 

 have seen, the growth of the brain in early childhood is very 

 rapid. As years advance, the increase in general bulk is not 

 so marked. There is usually, however, a continuous growth, 

 but it is largely confined to the gray matter. As in other 

 structures of the body, so in the brain, proper exercise is 

 necessary. The amount of gray matter, with the correspond- 

 ing amount of intellectual strength, depends largely on a due 

 exercise of the faculties of the mind. The amount and kind 

 of exercise should be regulated by those properly trained and 



