Now when the tubercle bacilli have settled in the lungs, they cause various symptoms. One of the most frequent is _cough_. In the beginning of the disease a short, clear but light, very often dry cough appears. During the further development of pulmonary consumption the cough becomes more periodic; it appears early after awaking, in the afternoon after dinner, and evenings at lying down; it may disappear entirely in the meantime or may be light only; but then as a rule it is no longer dry, but may be attended by expectorations of a varied nature. [Illustration: Section of a tuberculous knot in the lungs, in which two cavities are seen filled with numerous bacilli. The bacilli distinctly appear as dark lines as a result of the coloring. Enlargement 900.] [Illustration: Tubercle bacilli, Enlargement 2000. To the left bacilli without spores, to the right bacilli with colorless sections which are thought to be spores.] The tubercle bacilli destroy the lung tissue and change it into pus, which is coughed out. In this way larger and smaller cavities are formed in the lungs; finally the cavities may even take more space than the remaining lung tissue. When cavities have already been formed, coughing comes easy and with abundant expectoration. Toward the end of life the coughing and spitting stops as a result of the extreme feebleness and weakness. The violence and frequency of the cough depends mainly whether the larger bronchial tubes and the trachea are affected; the more this is the case, the more violent the inclination to cough. Further the strength of the cough depends on the excitability of the patient; the greater this is, the more as a rule will he cough. Sometimes the position of the patient is of influence; if he lies mostly on the diseased side the expectoration becomes more difficult and coughing increases. Coughing is generally that symptom which soonest attracts the attention of the patient and his surroundings. For that very reason consumption is in its beginning stages easily confounded with such other diseases as are also accompanied by cough. At the same time we know of exceptional cases where cough was entirely absent in the first stages of the disease, or was at least so slight that it was overlooked, and under such conditions the pale and poor appearance and reduced strength is mistaken for chlorosis or some other anaemic affection, also the existing febrile excitements are wrongly judged, or on account of lack of appetite or light derangements of the stomach a stomachic affection is surmised, until suddenly a hemorrhage of the lungs clearly defines the true nature of the ailment.