NERVOUS SYSTEM 



4121 



NET 



other being made through a minor nerve cen- 

 ter. This is explained under REFLEX ACTION 

 (which see). 



Cranial Nerves. Twelve pairs of nerves 

 branch off directly from the brain and reach 

 the muscles and other organs through openings 

 in the skull. The following pairs are of interest 

 to the general reader: The first pair are the 

 nerves of smell (olfactory); the second, the 

 nerves of sight (optic), and the third, the nerves 

 which control the movements of the eye and 

 the contracting of the iris to accommodate the 

 pupil to the intensity of light. These are the 

 motor nerves of the eye. One branch of these 

 nerves controls the movements of the upper 

 eyelid. The eighth pair are the nerves of hear- 

 ing (auditory), and the ninth, the nerves of 

 taste (glosso-pharyngeal). The tenth pair are 

 often called the pneumogastric nerves. They 

 are distributed to the pharynx, windpipe, lungs, 

 heart, stomach and other vital organs, thus 

 forming the connection between the sympa- 

 thetic and the cerebrospinal systems. It is 

 through the action of these nerves that mental 

 states affect the vital organs. Fear, for in- 

 stance, lessens the number of heart beats, and 

 melancholy influences digestion. The nerves 

 of the twelfth pair (hypoglossal) are distrib- 

 uted to the tongue and control the movements 

 of that organ. 



Sympathetic System. The nerves of the 

 sympathetic system extend to the heart, lungs, 

 stomach, intestines and other vital organs, 

 whose action they control. These nerves 

 branch off from the spinal nerves not far from 

 the spinal column and enter a row of ganglia 

 on each side of it. Each ganglion is connected 

 with the one above and the one below it. After 

 MU the ganglia the nerves form many large 

 and intricate networks called plexuses. The 

 1 1 most, the solar plexus, lies just back of the 

 stomach. A blow on the stomach may paralyze 

 the nerves of this plexus and cause death. The 

 4 of tins system so bind together the vital 

 organs that any injury or disease affecting one 

 organ affects all. Because these organs seem 

 to sympathize with each other the term sym- 

 pathetic was applied to this system, but it has 

 little significance. These nerves act more slowly 

 i those of the spinal system. Injury to a 

 spinal nerve is instantly known, but pains 

 caused by indigestion may not be felt until 

 il hours .< meal is eaten. 



Hygiene. The brain and nerves are the most 



ite body structures. They are the most 



easily injured and the most difficult to restore 



to a state of health. The first requisite to the 

 health of the nervous system is an ample sup- 

 ply of pure blood. One-fifth of the blood goes 

 to the brain and proportionate quantities are 

 required for the nourishment of the nerves, 

 consequently one who desires to maintain his 

 nerves in a normal condition should eat plain, 

 nutritious food and take plenty of exercise in 

 the open air. 



Overwork, either physical or mental, subjects 

 the nerves to an unnatural strain and should 

 be avoided (see FATIGUE). Sleep is one of the 

 best restorers of nervous energy. Stimulants, 

 narcotics and drugs are injurious and should not 

 be used except under the direction of a phy- 

 sician. WJ.R. 



Related Subjects. The following articles are 

 closely related to this subject, and reading them 

 will add interest to it: 

 Blood Health Habits 



Brain Narcotic 



Breath and Breathing Reflex Action 

 Ear Senses, Special 



Education, subtitle Sleep 



Hygiene of Education Taste 

 Eye 



NEST. See BIRD, subtitle Nests of the Birds. 



NES'TOR, a Greek hero, the son of Neleus 

 and Chloris, king and queen of Pylos in Mes- 

 senia. While he was away on a visit to Gerenia, 

 Hercules killed his father and brother, because 

 Neleus refused to purify him after the murder 

 of Iphitus (see HERCULES). Nestor escaped 

 only because he was away. He became a great 

 warrior and took part in the battle between the 

 Centaurs and the Lapithae. According to some 

 writers he was one of the huntsmen who helped 

 slay the great Calydonian boar, and a member 

 of the Argonautic expedition (see ARGONAUTS). 

 During the Trojan War, although he was an 

 old man and could not fight, he was one of the 

 wisest of the Greek council; this tradition of 

 his wisdom has been preserved in the figurative 

 use of the name Nestor as a synonym for one 

 who is very farseeing and prudent. 



NET, the name of a fabric with an open 

 weave, made of the various threads used in 

 textiles, from the finest silk to the coarsest 

 hemp. The spaces between the threads are 

 called the meshes, and the threads are knotted 

 at the intersections, to keep the meshes a uni- 

 i size. Net fabrics are used for numerous 

 purposes. They are made into nets for catch- 

 ing fish, animals and insects, they serve for 

 hammocks, screens and various domestic pur- 

 poses, and for the daintiest of women's apparel. 

 Wire netting is used to fence poult 



