314 HOW DOES THE HUMAN MACHINE DO ITS WORK? 



provides the machine properly with oxygen so that the fuel will 

 be oxidized; and the products of oxidation are carried away, as 

 well as other waste materials which might harm the effectiveness 

 of the machine. Most important of all, the human machine is 

 able to repair itself. 



No boy or girl can go into the big game of life and expect to be 

 a helpful member of society with an insufficient knowledge of the 

 human machine. Neglect or lack of proper care of our bodies may 

 defeat some of our life's fondest ambitions. The efficient citizen 

 should be the healthy citizen. 



PROBLEM I. WHAT IS THE GENERAL STRUCTURE OF THE 

 HUMAN BODY? 



Laboratory Exercise. The structure of the human body. Use 



manikin or good chart. 



Note the covering of skin. Can you think of any uses for this 

 structure? What general uses would the muscles have? Note their 

 position with reference to the skeleton and the organs of the body 

 cavity. Take off the covering and examine the organs within the 

 body cavity. The thin layer of muscles that separates the heart and 

 lungs from the abdominal cavity is the diaphragm. Use a good text 

 figure to locate the parts of the digestive tract : stomach, small and 

 large intestines, liver, and pancreas. Locate the kidneys, and the 

 tubes (ureters) leading to the bladder and thence outside of the body. 



Skin and muscles. If we are thinking of the body as a machine 

 which does work, then it is obvious that, while the skin is partly a 

 protective organ, the muscles are structures by which work is largely 

 accomplished. The diagram (p. 320) shows that they are attached 

 to bones which serve as levers and thus accomplish movement. 



Other body structures. In spaces between the muscles are 

 found various other structures — blood vessels, which carry blood 

 to and from the great pumping station, the heart; connective 

 tissue, which holds groups of muscle or other cells together; fat 

 cells, scattered in various parts of the body ; various gland cells, 

 which manufacture the enzymes which digest our foods ; and the 

 cells of the nervous system, which aid in directing the various 

 parts of the body. 



Body cavity. Within the cover of skin, bone, and muscle is a 

 cavity filled with various organs. A thin wall of muscle called 



