184 GENERAL SCIENCE 



The grape sugar or glucose dissolves readily, and passes into the 

 blood, where the hydrogen and the carbon oxidize, producing large 

 quantities of heat and energy. This process of oxidation is some- 

 times called wet burning. 



How the Body Supplies Oxygen for the Burning of Food. The 

 blood gets its oxygen from the atmosphere through the process of 

 respiration. The lungs are composed of a great mass of air passages 

 and air sacs (about 725,000,000). Because of the great number of 

 blood vessels in the lungs, as much blood goes to the lungs as goes to 

 the remainder of the body at any one time. The walls of the air 

 sacs are very thin. The oxygen passes through the walls of the 

 sacs and enters the blood. In the blood little red corpuscles contain- 

 ing a substance called hemoglobin act as the carriers of the oxygen. 

 The hemoglobin unites with the oxygen, or, in other words, takes a 

 load of oxygen away from the lungs and delivers it to the cells of 

 the body. When the stomach is filled with. a hearty meal a great 

 many red corpuscles go to the vicinity of the stomach and intestines 

 where the food is entering the blood. The oxygen oxidizes the food, 

 making it give off large quantities of heat and energy. 



A part of the proteid food is used to build up the cells of the 

 body; the rest is oxidized or burned up, forming carbon dioxide, 

 water, and uric acid. The carbohydrates and fats, when oxidized, 

 form carbon dioxide and water. All of our foods, upon burning, 

 give us large quantities of heat and energy which are required to 

 maintain the body temperature and give us strength to do our 

 work. 



Animals that Store away Food. Some animals hibernate all 

 winter by storing fat in the body and using it up during the winter 

 sleep. Camels store fat in the humps on their backs that they may 

 be able to travel for days in the desert without food. 



The Removal of Carbon Dioxide from the Body. All the carbon 

 dioxide produced by the burning of food in the body must be removed. 

 The carbon dioxide is dissolved by the plasma, the chief element 

 of the blood, composed mainly of water. The function of the 

 plasma is to carry waste. The hemoglobin of the red corpuscles 

 also assists the blood plasma in disposing of the carbon dioxide. 

 Its chief function, however, is to carry oxygen when the blood 



