4 ORGANS AND TISSUES. 



teaches what is good and what hurtful to our bodies in 

 other words, how we may best preserve our health is 

 known as Hygiene. 



5. Organs and Functions. The separate parts of which 

 the body is made up are called organs: thus the eye is the 

 organ of sight, the teeth are organs of chewing, the stom- 

 ach is an organ of digestion. The use of any organ is 

 spoken of as its function : thus the function of the eye is 

 seeing, of the ear hearing, of the hand grasping. 



6. The Structure of Organs. The human body, like a 

 watch, not only has numerous parts, but these parts are 

 made of different materials. Taking the hand, for ex- 

 ample, we observe on the outside, skin, nails, and hairs. 

 If the skin were removed we should see below it some 

 fat, just like that in beef and mutton. Under the fat, in 

 the ball of the thumb you would find some red flesh, 

 called muscle, which answers to the lean of meat. Be- 

 neath all the rest would be white hard bones. At the 

 finger-joints where the ends of separate bones come near 

 together you would see covering each a thin layer of 

 gristle or cartilage. And binding together the skin and 

 fat and muscles and bones would be found a stringy sub- 

 stance which, as it unites all the rest, is called the con- 

 nective material. 



7. Tissues. Each kind of material used in constructing 

 the body is called a tissue: and each tissue has its own 

 peculiar properties. Connective tissue is tough and suited 



5. What is an organ ? Give examples. What is a function ? Il- 

 lustrate. 



6. What is meant by the structure of an organ ? Describe the 

 structure of the hand. 



7. What is a tissue? Name and describe some tissues. Name 

 some liquids of the body. 



