8. Pulmonary Tuberculosis.--The sputum is variable. In the earliest stages it may be scanty and almost purely mucoid, with an occasional yellow flake, or there may be only a very small mucopurulent mass. When the quantity is very small there may be no cough, the sputum reaching the larynx by action of the bronchial cilia. This is not well enough recognized by practitioners. A careful inspection of all the sputum brought up by the patient on several successive days, and a microscopic examination of all yellow portions, will not infrequently establish a diagnosis of tuberculosis when physical signs are negative. {46} Tubercle bacilli will sometimes be found in large numbers at this stage. Blood-streaked sputum is strongly suggestive of tuberculosis, and is more common in the early stages than later. The sputum of more advanced cases resembles that of chronic bronchitis, with the addition of tubercle bacilli and elastic fibers. Caseous particles containing immense numbers of the bacilli are common. Far-advanced cases with large cavities often show rather firm, spheric or ovoid masses of thick pus in a thin fluid--the so-called "globular sputum." These globular masses usually contain many tubercle bacilli. {47} CHAPTER II THE URINE Preliminary Considerations.--The urine is an aqueous solution of various organic and inorganic substances. It is probably both a secretion and an excretion. Most of the substances in solution are either waste-products from the body metabolism or products derived directly from the foods eaten. Normally, the total amount of solid constituents carried off in twenty-four hours is about 60 gm., of which the organic substances make up about 35 gm. and the inorganic about 25 gm. The chief organic constituents are urea and uric acid. Urea constitutes about one-half of all the solids, or about 30 gm. in twenty-four hours. The chief inorganic constituents are the chlorids, phosphates, and sulphates. The chlorids, practically all in the form of sodium chlorid, constitute one-half, or about 13 gm., in twenty-four hours. Certain substances appear in the urine only in pathologic conditions. The most important of these are proteids, sugars, acetone and related substances, bile, hemoglobin, and the diazo substances. In addition to the substances in solution all urines contain various microscopic structures.