18 DIGESTION DIAGRAM 1. 



oesophagus (see diagram 2) through which the food passes, and 

 with the larynx, where the air for respiration enters. The food 

 passes from the throat into the oesophagus, and through that 

 into the stomach. There it changes its nature entirely, and 

 acquires an exceedingly disagreeable taste .and odour. "We 

 perceive this when we vomit ; the stomach rejects its contents, 

 and we can already perceive how greatly the food has been 

 altered. It is still more altered when it passes into the intes- 

 tines, where it is mixed with the bile. Then it is absorbed by 

 the surface of the intestines, and is converted into blood ; and 

 this in its turn becomes flesh, muscles, tendons, bones, car- 

 tilages, skin, hair, nails, humours ; in short, all the sub- 

 stances which compose the various organs of the body. What 

 is not thus absorbed and transformed is expelled from the body. 



NERVES AND BRAIN. The nerves are small white cords which 

 penetrate the whole body, and convey our wishes to every part. 

 If we wish to move the foot or hand, it is by means of the 

 nerves that our will contracts the muscles which move the hand 

 or foot. We also feel by means of the nerves. If the nerves 

 of the leg, for instance, have been severed by a wound, the leg 

 immediately becomes insensible and incapable of movement; 

 it is, as doctors say, paralysed. 



The nerves sometimes cause great suffering, and produce 

 what is called neuralgia. 



All the nerves in the body return to the spinal cord and to 

 the brain, which is a continuation of it. The spinal cord and 

 the brain are composed of a very soft substance, fortunately 

 protected by the skull and the vertebra, for the least touch 

 which it sustains is always followed by the most serious con- 

 sequences. Part of this substance is grey, and the rest white. 

 The first forms the surface of the brain, the second is in 

 the centre. The whole surface of the brain is covered with 

 large folds, which are called convolutions. 



The brain is the organ by which we feel, think, remember, 

 or decide upon any action, such as reaching out the arm, or 



