THE NERVOUS SYSTEM 129 



diseased, the others do not continue to work and tax 

 the strength of the ailing organ. 



How the Sympathetic and Cerebro-spinal Nerves Differ. 

 The ganglionic nerves (i) contain mostly gray fibers ; 



(2) pass through ganglia after leaving the spinal cord ; 



(3) control the unconscious activities of the body ; (4) pass 

 to organs which contain slow-acting involuntary muscles, 

 not to sense organs and quick-acting voluntary muscles ; 

 (5) transmit impulses sloivly (about 20 ft. instead of 100 

 ft. per second). Crawfish and insects have hardly more 

 than the ganglionic system of nerves (Animal Biology, 

 Figs. 92, 132, 197). 



Examples of the Supervisory Functions of the Sympa- 

 thetic System. - - Regulation of the heart beat and of the 

 size of the blood vessels ; secretion of sweat glands ; con- 

 traction of pupils of eyes in a brigrBbght; peristalsis. 



Examples of Sympathetic Nerve Impulses reaching Con- 

 sciousness. Pain in colic and cramps; "heartburn' 

 (pain in stomach from indigestion); backache (from 

 nerves in organs prolapsed by tight clothing pulling upon 

 their attachments at spine) ; hunger ; thirst. 



The Mind and Health. --A contented or peaceful mind is indispen- 

 sable to soundest health. Worry causes difficult breathing with bated 

 breath. Happiness brings full, easy breathing. Biological study of 

 physiology shows the futility of making health a care or anxiety, and 

 teaches "'no meddling 1 ' with the body, whether by stimulating it, drug- 

 ging it, deforming it, overheating it, half smothering it in close rooms, 

 cultivating artificial instincts, etc. If the body degenerates through 

 wrong living, and disease ensues, a new way of living is needed, not 

 some quick and wonderful remedy. The new life will renew the body 

 and nothing else can. 



HYGIENE OF THE NERVOUS SYSTEM 



Necessity of Food, Fresh Air, and Rest for Sound Nerves. 

 - The health of the nerves depends upon a free supply of 

 K 



