All of us, at one time or another, have suffered from fever, aches. vomiting, nausea. diarrhoea, flu, cold, general weaknessetc. Illness can arise from a number of factors, sucn asfailure of some part of the machine, i.e. our body, or inheritance of some tendency or malfunction from the family, or problems due to aging or due to some infection etc. As you have learnt in the previous units, it can also be due to some deficiency or even lack of nourishment. You may be familiar with the names of some of the serious diseases such as cancer, tuberculosis, typhoid etc. A recent addition to the deadly diseases is the one called AIDS in which the body loses all natural power to fight a disease. We could say that a disease is a departure from the state of health. Any variation in the normal structure or function of a tissue or an organ of the body could mean disease. Doctors have various methods and instruments to f!nd out if a person is suffering from any disease These are :
i) physical examination, like testing of eyesight or hearing the sound of heart beats, or observing the movement of the limbs,
ii) biochemical tests performed on the tissues and fluids of the body, like testing if there is sugar h the urine or too much fat in the blood,
iii) microscopic examination of the body fluids and/or excreta- the familiar examples are blood, and stool test etc.,
iv) use of biophysical methods like X-rays, to detect fractures of bones, or to examine the condition of the lungs,
v) surgery and other methods to locate diseased organs inside the body.