There are glands under our skin called sebaceous glands which secrete a kind of oily liquid on our skin. This keeps our skin oily and protects it from going dry.
To see the effects of this secretion, take some surgical spirit and using some cotton wipe the palm of your right hand. After that, tell one of your friends to put one or two drops of a detergent solution on the palm and also on the other palm which had not been wiped. You will find that the detergent solution is spreading on the palm which had been wiped while on the other palm it does not spread.
The Thickness of Human Hair
There will be a microscope in your school laboratory. With the help of that you can do this experiment.
Ask an adult person to cut two hairs from your head.
Place them under the microscope and study the characters. Then get a few samples of hair from other persons and then study them also under the microscope.
You will find that there is a lot of characteristic features to individual hairs, some being thin and some thicker than others.