THE BLOOD AND THE NERVES 205 



muscles, lessens the blood supply of the surface of the 

 body. Wet garments, too, have a similar effect, 

 because some of the heat of the body next them is 

 used in evaporating the water. On that account, 

 the temperature of the skin is lowered, the amount 

 of blood being made less, as the cold contracts the 

 arterial muscles. Binding the arteries by wearing 

 tight garters, belts, corsets, or other clothing is a 

 hindrance to free circulation that all can avoid. How 

 foolish we should think a hungry person who obstructed 

 his walks or doors so that little or no food could be 

 brought to him by the delivery man ! Keeping blood 

 from the hungry tissues by wearing tight clothing of 

 any kind is just as unwise. 



An acquaintance with our marvelous telegraph 

 system is another important step toward a better 

 knowledge of how we may protect Jack's House. How 

 curious ! Have we really anything like a telegraph sys- 

 tem in our bodies? We certainly have, and a more 

 remarkable one than has ever been made by man. The 

 central office is the brain, and the main wire, the spinal 

 cord. This wire is protected by the vertebraB of the 

 spine (backbone) through which it runs. Numerous 

 smaller wires, or nerves, branch off from this all along 

 its course, dividing and subdividing until every part 

 of the body, no matter how small or how distant, is 

 reached. Sub-stations, called ganglia, are situated in 

 various parts of the body, being especially numerous 

 in the back. 



