CONGESTION OF THE LUNGS 49 



excitement, exercise, etc. In some diseases it is varied in 

 tone, becoming louder and more prolonged. 



4. Percussion.— This is performed by the use of the per- 

 cussion hammer and pleximeter or by one hand placed 

 against the chest wall and tapped with the fingers of the 

 other hand. The normal sounds of a healthy lung are heard 

 all over the thorax, the volume of sound depending on the 

 thickness of the lung at the particular part being examined. 

 The normal sound is clear, loud and resonant as distinguished 

 from the tympanitic, dull or solid sound of disease. Tym- 

 panitic sounds are heard in the following conditions: '(a) 

 Emphysema, (b) pneumothorax, (c) cavities in the lungs, 

 (d) in collapse of the pulmonary tissue from a retraction of 

 the lungs in the presence of pleuritic exudates. The col- 

 lapsed lung floats upon the surface of the fluid above the line 

 of dulness and on percussion emits a tympanitic sound, (e) 

 In the first and last stages of pneumonias. Dull or flat 

 sounds are heard over hepatized areas of the lungs, chronic 

 interstitial pneumonia; tumors in the lungs, and hydro- 

 thorax. 



CONGESTION OF THE LUNGS. 



Hyperemia of the Lungs. 



Definition.— An excessive or abnormal accumulation of 

 blood in the lungs. Hyperemia may be either active or 

 passive. 



Active Congestion.— Etiology.— It is found in the early 

 stages of all inflammatory conditions of the lungs and pleura. 

 Occasionally it may be due to inhalations of irritating gases, 

 smoke, acid fumes, etc., or may result from cold. 



Pathology.— The lungs are dark red in color; on cross- 

 section blood escapes from the cut surface. The tissue will 

 float in water. 



Symptoms.— Active congestion of the lungs is characterized 

 by its sudden onset, beginning as a rule with a chill and 

 rapidly developing dyspnea accompanied by a short, dry 

 cough and a rapid, full pulse. The animal often assumes a 

 sitting posture with elbows held outwardly, ribs elevated 

 4 



