438 CHRONIC INFECTIOUS DISEASES 



years elapse before appreciable symptoms appear. In cattle 

 tuberculosis inducing clinical symptoms affects the following 

 organs or tracts: 



(a) Lungs. — Cough is often a noticeable symptom. The 

 cough is usually short, dry, and infrequent, occurring at 

 first early in the morning when the cattle are driven up to 

 feed or milk. Sometimes moving the animals, a cold drink 

 of water, or a chilly draft of air (opening the stable door) 

 induces it. In an occasional case the cough is paroxysmal. 

 During the act of coughing a fine spray is ejected from the 

 nose and mouth, and following it a viscid, bronchial exudate . 

 is swallowed. Sometimes a portion of this exudate is retained 

 for a time in the mouth and pharynx, from whence it may 

 be removed with the hand. (See Diagnosis.) 



Dyspnea is usually not a prominent symptom when the 

 patient is at rest. After brisk motion, however, the respira- 

 tions become abnormally rapid and labored. 



Percussion. — ^As the tubercles in the lung are generally 

 surrounded by air-containing alveoli, percussion is usually 

 negative. Only when large areas (at least 10 cm. broad) 

 of solidification are superficially located and the thoracic 

 wall relatively thin, is dulness noted. 



Auscultation is very often negative. Especially after 

 exercise in some cases, bronchial breathing and rales are 

 heard. The rales are either dry or moist, depending upon 

 whether the exudate is tough-viscid or more fluid in char- 

 acter. Dry rales, as a rule, predominate and are heard over 

 the whole field of auscultation. 



If the pleura is also involved (tubercular pleuritis, pearl 

 disease) the patient may show pain on pressure over the 

 ribs and percussion induces coughing. Friction sounds on 

 auscultation can rarely be distinguished. Generally the 

 clinical symptoms of tubercular pleurisy are too vague to 

 be of diagnostic value. 



Appetite. — In the earlier stages the appetite is retained, 

 but toward the end (when the animal becomes emaciated) 

 it is lost. 



Loss of Flesh. — In the later stages of pulmonary tuber- 

 culosis the animal begins to lose flesh notwithstanding good 



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