THE GOVERNOR OP THE BODY 247 



would be impossible to hold our breath until we suffocated. 

 This automatic action of the body is of immense advantage 

 in that it relieves us of all necessity for supervision of most, 

 bodily processes, leaving the mind free to attend to the more 

 important matters connected with mentality. The muscles 

 under the control of the will are very different in appearance 

 from those that are connected with involuntary action. The 

 voluntary muscles are striped crosswise of their length while 

 the involuntary muscles are plain. Since these latter are not 

 attached to the bones they also lack tendons. Their move- 

 ments are controlled largely by the medulla and the spinal 

 cord, but some, especially those of the heart, have some power 

 to contract and expand by themselves. 



211. Reflex Action. The spinal cord not only transmits 

 nervous impulses to and from the brain, but it may act like 

 the brain on occasion and send out impulses in response to 

 sensations without waiting for the brain to act. Thus, when 

 a finger is injured, we pull it out of danger before we can think 

 about the matter. Sensations may even cause such actions 

 in distant and different parts of the body, as when a tickling 

 in the nose causes us to sneeze or some disagreeable sight or 

 sound may cause fainting. Actions of this kind are called 

 reflex actions. Many acts which are conscious and voluntary 

 at the beginning may later become reflex, as in walking, skat- 

 ing, bicycling, and even piano playing. Such actions, though 

 ordinarily reflex, may, however, be controlled by the will. 

 The actions of many animals are reflex and the lower the 

 animal in the scale of life, the less important do the higher 

 centers of the brain become. The advantages of reflex action 

 are that they automatically withdraw the body from injury 

 and, like the involuntary actions, relieve the higher nerve 

 centers of the routine work of running the body. 



212. Pain and the Nerves. Pain may be regarded as an 

 over stimulation of the end organs. The sensations are 



