Many symptoms can be detected only by methods requiring scientific apparatus as well as the knowledge and skill of a physician, but very pronounced symptoms are generally evident to anyone. The neighbors do not need to be told when a person has advanced tuberculosis; neither is an expert required to see that something ails a man with a broken leg. Furthermore less pronounced symptoms may often be clearly seen by any observant person, even by those not specially trained. Accordingly it is important for every woman who has charge of others, sick or well, to form the habit of noticing unusual appearances of any kind. This habit is one that most people must take pains to acquire, because people generally see only the things that their own experience in life has taught them to see. An added difficulty is the fact that when illness begins it is not a trained observer, but the untrained sufferer or untrained member of his family who decides whether to send for the doctor and thus to set in motion the machinery for treatment and cure. All the training and experience of a physician are required in order to decide what symptoms indicate, and to prescribe proper remedies. Diagnosis, or the process of determining the nature of illness from the symptoms observed, is often exceedingly difficult; it must take into consideration not one symptom only but the presence or absence of a number of symptoms. Untrained persons who attempt to make diagnoses are frequently led astray by the fact that actual causes of trouble may be situated far from the places where symptoms are felt or observed. For instance, the real cause of headache may lie in a region far removed from the head; and so-called heart-burn, which is caused by disordered digestion, has nothing to do with the heart. Again, an early symptom of tuberculosis of the hip joint is pain under the knee; a mother is clearly not doing the best thing when she assumes that any pain in a joint means rheumatism, and therefore doses her suffering child with the medicine that "helped" his rheumatic grandfather. No untrained person is equipped to make a diagnosis, and still less to prescribe medicine or treatment.