340 _ PHYSIOLOGY AND HEALTH. 



than when they require the aid of mental action. Thus, 

 when we walk, if we lift the foot and place it down at each 

 step by a special effort of the mind, we shall be more wearied 

 than when we walk, as we usually do, without a special vo- 

 lition for each step, and have the mind free to attend to other 

 matters. It is easy to see this difference of effect of exertion 

 in the beginner and the practised performer of any work or 

 art. The self-possessed dancer, who moves with careless 

 ease through his figures, is less exhausted than the timid, 

 cautious dancer, who anxiously watches every step. Both 

 of these may move with the same energy, yet the one who 

 added mental action and care to his muscular exercise drew 

 more upon the nervous energies than the other, who exerted 

 the muscles alone. 



780. Every function of every organ is dependent upon 

 the nerves for its power. The tongue has a nerve of taste, 

 one of common sensibility, and another of motion. The 

 eye has one nerve of sight, another of motion. The secre* 

 tions of the saliva, of the tears, and of the gastric juice, &/c., 

 are dependent upon their peculiar nerves to stimulate the 

 processes. Each one of these operations must have its own 

 nerve, and that must be in good health, and connected with 

 the brain directly or through the spinal cord. If this ner- 

 vous connection is disturbed or suspended, the function is 

 impaired or fails. 



CHAPTER V. 



Brain presides over all Organs and Functions. When it is impaired, 

 all Organs and Functions impaired. Not sensitive. Subject 

 to Laws of Body. When pressed, general Sensibility and Pow- 

 er suspended. Subject to Growth and Decay. Has large Sup- 

 ply of Blood. Change of its Particles increased by Exercise. 

 Fatigued with Action. Sleep. 



781. THE brain is the presiding genius over all the pow- 

 ers and Actions of life. It stands above all and over all, 

 giving energy to, and directing the motions, ana operations 



