CONSTITUENTS OF FOOD. 91 



If carrots are withheld, a bran mash, which is generally 

 allowed once or twice a week, would add to the water in the 

 food. The addition of water confers laxative properties on 

 the bran, which, when given dry, has not this effect. 



A full diet containing an undue proportion of water would 

 diminish the power of breathing by increasing the volume of 

 the stomach and intestines. We may here note that the 

 interior of the body is divided by the diaphragm (midriff) into 

 two cavities : the thoracic cavity (chest), and the abdominal 

 cavity (abdomen) ; the former containing the lungs and heart ; 

 and the latter, the stomach, intestines, liver, spleen, bladder, 

 and other organs. The front portion of the stomach and 

 intestines lies against the rear surface of the diaphragm, which 

 is a cone-shaped muscle that has its apex pointing forwards, 

 and its base attached to the spine and to the ends of the 

 ribs. The act of inspiration (taking air into the lungs) is 

 effected by muscles which increase the size of the thoracic 

 cavity. By diminishing the pressure of air in that cavity, 

 these muscles cause air to pass from outside, through the 

 nostrils, windpipe and bronchial tubes, and to enter the air- 

 cells of the lungs, which then become inflated. Speaking 

 generally, the muscles in question may be divided into two 

 sets, namely, those which by contracting enlarge the size of 

 the chest by drawing the ribs forward (thoracic breathing), 

 and the diaphragm, which by contracting performs a similar 

 office by pushing the contents of the abdomen in a backward 

 direction (abdominal breathing). Expiration (expulsion of air 

 from the lungs) takes place by the two sets of muscles ceasing 

 to contract and thus allowing the ribs to fall back into their 

 previous position, while the diaphragm and its contents move 

 forward into the chest. As the action of breathing depends on 

 the ability possessed by the chest of increasing its internal 

 capacity during inspiration, it follows that the greater the bulk 

 of the stomach and intestines, the more will the power of 



