48 DISEASES OF THE LUNGS 



which the ear is placed. With the phonendoscope the sounds 

 are made more audible and distinct. 



The normal sounds of the lungs are: (a) The vesicular; 

 (6) bronchial, and (c) the expiratory, (a) The vesicular sound 

 normally is a soft, regular, blowing sound caused by the air 

 passing into the alveoli and distending them. It is most dis- 

 tinct in emaciated animals and where the lung tissue is in close 

 contact with the thoracic walls. It is normally increased by 

 excitement or exercise and is always more distinct in puppies 

 than in older dogs. The vesicular sound is modified in the 

 following pathological conditions: Increased in dyspnea in 

 the healthy portion of the lung, in tracheitis and in bronchitis; 

 decreased in stenosis of the upper air passages; in certain 

 stages of catarrhal pneumonia; emphysema of the lungs; 

 hydrothorax; swelling and thickening of the skin and muscles 

 of the thorax and in certain poisonings. 



(b) Bronchial respiratory sounds are best recognized by 

 placing the phonendoscope directly over the trachea at its 

 entrance to the chest. These sounds are normal in the larynx 

 and trachea, but their appearance in the thorax is significant 

 of disease. Bronchial respiratory sounds are increased by 

 secretions in the smaller bronchi, as in catarrhal pneumonia; 

 compression of the lungs by pleuritic exudate; laryngitis, 

 tracheitis and bronchitis. 



Irregular bronchial sounds are caused by the secretions 

 being carried to and fro by the passage of the air. They are 

 dry (wheezing) where there is a small quantity of mucus 

 . adherent to the mucous membrane. These sounds (wheezing) 

 occur mostly in the smaller bronchi, while the moist, bubbling 

 rales (sonorous) emanate from the larger bronchi where they 

 are produced by the collection of secretions. Cavities in the 

 lungs also produce them. Bronchial sounds are important 

 in determining the existence, extent and character of trache- 

 itis and bronchitis. When sibilant {wheezing) sounds are 

 prominent it indicates that the infection extends into the 

 bronchioli. 



(c) Expiratory sounds are produced by the rapid expulsion 

 of air from the lungs, and in normal conditions are hardly 

 perceptible, except in puppies. This sound is increased by 



