180 Collection of Air in the Pleural Cavity. 



necessary for the production of t^aiipanitic sound will be pres- 

 ent under these conditions. In open pneumothorax one com- 

 monly also hears the noise of the cracked pot. The percussion 

 sound of a closed pneumothorax, in total or considerable pul- 

 monary collapse, remains atympanitie in large animals; it be- 

 comes, however, distinctly t^mipanitic in small animals, and also 

 in large animals if conditions have brought about the forma- 

 tion of a small column of air. 



One usually hears a metallic sound on ordinary percussion, 

 frequently only on auscultating or on percussion with two hard 

 objects ; this is, as a rule, audii)le over the whole of one-half of 

 the thorax. If adhesions have previously been formed, or if 

 rapid closure of the opening has permitted the entrance of only 

 an inconsiderable amount of air, the metallic sound is heard over 

 a limited area onlj^ When there is an open communication of 

 the pleural cavity with the air passages, one hears the metallic 

 sound, even at a distance, in smaller animals after opening their 

 mouth. The percussion sound of the chest may, posteriorly, on 

 the affected side be followed up to the costal arch; the same 

 occurs, however, on the healthy side in consequence of a com- 

 pensatory distention of the lung on the healthy side. 



After the development of pleurisy with effusion, one can 

 demonstrate dullness to a variable extent with an upward hori- 

 zontal boundary line ; here there is no metallic sound. 



Auscultation demonstrates conditions which vary from case 

 to case. Sometimes one hears no lireathing sounds at all in con- 

 sequence of intense collapse of the lungs ; as a rule, however, the 

 breathing sounds penetrate through a not overly thick column 

 of air. One then hears bronchial, possibly amphoric breath- 

 ing; usually, however, only a metallic sound. If there is fluid 

 and air between the layers of the pleura, one hears metallic 

 splashing with every respiratory movemeiit, which becomes still 

 more intense in sudden movements or in shaking of the animals. 

 In exceptional cases, one sometimes hears dripping sounds. 



The heart beat is not felt at all on the affected side, or only 

 faintly; the heart sounds are occasionally accompanied by a me- 

 tallic note. 



Course and Prognosis. The described symptoms usually 

 last only a short time, especially if pneumothorax follows an 

 already existing pneumonia or pleurisy; however, even in ani- 

 mals which were previously well, pleurisy usually develops soon 

 and brings about a fatal issue. Pneumothorax from injury or 

 rupture of a healthy lung ends in recovery somewhat more fre- 

 quently; one due to penetrating injury of the thoracic wall 

 rarely, i. e., when infection of the pleura has not occurred. The 

 air is absorbed in such cases after closure of the injury, and tlie 

 lungs again expand. 



Diagnosis. Characteristic for pneumothorax is the metallic 

 sound present over a large portion of the thorax and brought 



