Most of us have a general idea of how the body tries to resist disease and what we can do to help it. The body is often thought if as a city,organized to keep most if it inhabitants happy and to protect itself from enemies, every member of the city has a piece work to do. Some of the inhabitants are chiefs and have very important work, but the most interesting thing about it is that no member if the city can do his work properly unless others do their share; the happiness of the whole city, and it ability to resist it enemies , depends not only in the chiefs, but also on the more humble citizens. A set of inhabitants (organs) working together for a special purpose is called a system.
THE ORGANISATION OF THE CITY:
The city had a king (the brain) and it deputies (the nerve centers), all these manage the business of the city and send orders to the chiefs and people.
THE COMMUNICATION SYSTEM:
This is a wonderful system by which messages are sent from place to place by the nerves. There are head offices and exchanges as in telephone and telegraph systems.
If the nerves get out of order the whole work of the city goes wrong and everyone becomes unhappy.
THE FOOD SYSTEM:
The city is supplied with food by the digestive system which provides that each members gets food in the firm which it likes. This system consist the mouth, stomach and inteztines.
THE TRANSPORT SYSTEM:
There is a very good system if transport (the circulation of blood) by which food is carried to different parts, and by which, when the city is invaded, soldiers are conveyed to the place of attack. It also carries away all refuse too.
THE SANITARY SYSTEM:
This system gets rid of material not wanted by the city. This system (the excretory syatem) is of great importance. It consist if the kidneys, the skin, the lungs and the bowels.
THE WORKING SYSTEM:
The work of the city is done by the bony and muscular systems together. The skeleton or bony system is the frame work of the whole. Unlike the framework of the house it is very flexible, as many joints if different kinds and can be moved in many ways. The power that makes the movement is supplied by the muscular system.
THE VENTILATION SYSTEM:
This supplies the city with one of the most important needs. It proper name is the respiratory system. By means of this, the gas called oxygen enters the body through the nose or mouth and gies to the lungs where, as will be seen, it does important work.
THE REPRODUCTIVE SYSTEM:
One of the most wonderful things about this city is that special part of it, the womb and ovaries, are able to lay a foundation of a new city. This it can only do with the help of new life (semen) from another city.
THE ARMY:
The city is well organised for defence.
There is a wall around it (the skin) with well guarded gates (nose and mouth). The soldiers are in the blood and when an enemy enters they are rushed to the fight. This causes tje part of attack to become full of blood (inflammation), and often the soldiers (white corpuscles) are killed and their dead bodies go to form a whitish matter called pus. It is very important that this soldiers must be strong and well nourished so that they may defeat an invader when it enters the body.
THE ENEMIES IF THE CITY:
These are worms, germs etc that are constantly trying to enter the city. They may try the main gates (mouth and nose) or may get through a hole in the wall (a scratch or cut in the skin).
One of the thing hygiene has to do is to teach us how to protect this gates and to strengthen the body against attack.
DEFENCE:
There are three ways in which we can help an attacked city:
