=COUGH= (_occurring in Bronchitis, Pneumonia, Consumption or Tuberculosis, Asthma, and Influenza or Grippe_).--Cough is a symptom of many disorders. It may be caused by irritation of any part of the breathing apparatus, as the nose, throat, windpipe, bronchial tubes, and (in pleurisy and pneumonia) covering membrane of the lung. The irritation which produces cough is commonly due either to congestion of the mucous membrane lining the air passages (in early stage of inflammation of these tissues), or to secretion of mucus or pus blocking them, which occurs in the later stages. Cough is caused by a sudden, violent expulsion of air from the chest following the drawing in of a deep breath. A loose cough is to be encouraged, as by its means mucus and other discharge is expelled from the air passages. A dry cough is seen in the early stages of various respiratory diseases, as bronchitis, pneumonia, pleurisy, consumption, whooping cough, and with irritation from enlarged tonsils and adenoids (see p. 61) occurring in children. Irritation produced by inhaling dust, or any irritation existing in the nose, ear, or throat may lead to this variety of cough. The dry cough accomplishes no good, and if continuous and excessive may do harm, and demands medicinal relief. =Bronchitis.=--Cough following or accompanying cold in the head and sore throat generally means bronchitis. The larynx or lower part of the throat ends just below the "Adam's apple" in the windpipe. The windpipe is about four and a half inches long and three-quarters to an inch in diameter, and terminates by dividing into the two bronchial tubes in the upper part of the chest. Each bronchial tube divides and subdivides in turn like the branches of a tree, the branches growing more numerous and smaller and smaller until they finally end in the microscopic air sacs or air cells of the lungs. The bronchial tubes convey air to the air cells, and in the latter the oxygen is absorbed into the blood, and carbonic acid is given up. Bronchitis is an inflammation of the mucous membrane lining these tubes. In cough of an ordinary cold only the mucous membrane of the windpipe and, perhaps, of the larger tubes is inflamed. This is a very mild disorder compared to inflammation of the smaller and more numerous tubes.