52 DISEASES OF THE LUNGS 



If the animal's condition will permit the use of a hydra- 

 gogue purgative, magnesium sulphate (8.0-10.0) is useful to 

 modify the circulation and remove fluid from it. This dose 

 may be repeated in twelve hours if sufficient action has not 

 taken place. 



PULMONARY EDEMA. 



Edema of the Lungs. 



Definition.— An effusion of serous fluid into the alveoli and 

 interstitial tissue of the lungs. 



Etiology.— Diseases of the heart (valvular insufficiency, 

 etc.) are the most frequent predisposing causes of pulmonary 

 edema, although it occurs as a secondary condition to chronic 

 pulmonary congestion, nephritis, cachexia, anemia and infec- 

 tious diseases (distemper, etc.). In the latter stages of dis- 

 temper pulmonary edema frequently develops when it is 

 often the immediate cause of death. Edema of the lungs 

 occasionally follows the administration of drugs (pilocarpin, 

 etc.). 



Pathology.— The lung is heavier and firmer than normal, 

 pale in color and pits on pressure. When incised a thin 

 serous fluid escapes. This may be clear or if there is conges- 

 tion present it may be stained with blood. Crepitation is 

 always lessened and small patches may be entirely airless. 

 The bronchi contain a frothy fluid. 



Symptoms.— The symptoms develop rapidly except in 

 those cases occurring as the terminal event in exhaustive 

 diseases in which the course is more gradual and the symp- 

 toms less pronounced. Severe dyspnea, which becomes 

 worse as the exudate accumulates is an important symptom. 

 The pulse is weak and small, the visible mucous membranes 

 are cyanotic and the extremities cold. A short, feeble cough 

 often accompanies the condition. The temperature is sub- 

 normal. There may be a frothy nasal discharge. Upon 

 auscultation various kinds of rales (fine, course or bubbling) 

 will be heard. Percussion reveals diminished normal reso- 

 nance with occasional small areas of tympany, especially over 

 the posterior part of the lungs. 



