Anatomical Changes. Symptoms. 179 



inspiration and close during expiration (valvular pneumotho- 

 rax), then the air pumped in on inspiration will rapidly com- 

 press the lungs and expand the wall of the thorax. If the opening 

 closes sooner or later (closed pneumothorax) the lungs will also 

 collapse proportionately to the amount of air entered. But on 

 account of the closure of the opening they will not become com- 

 pressed, the air is uniformly distril)uted around the external 

 and lower portions of the lungs, and can be absorbed later on. 

 With the air streaming in through the wall of the thorax 

 or from the air passages and always with air coming from 

 neighboring organs, bacteria get into the pleural cavity and 

 may lead to fibrinous, more usually to purulent, pleuritis. 



Anatomical Changes. Air does not stream outward or in- 

 ward in open pneumothorax after opening of the thoracic wall ; 

 it streams occasionally into the chest cavity in closed pneumo- 

 thorax and streams out with a hissing sound in valve pneumo- 

 thorax; it may then move a flame held before the opening. 

 If the trachea had been closed air-tight before an injury to the 

 lung, on opening the chest cavity, one can easily recognize the 

 collapse of the lungs as it occurred during life. We also usually 

 find the signs of serofibrinous (hydropneumothorax) or puru- 

 lent pleuritis (pyopneumothorax). The changes are usually 

 found in one, rarely in both pleural cavities. 



Symptoms. The sjanptoms of pneumothorax either set in 

 suddenly or they develop very gradually, according to whether 

 air got into the pleural cavity suddenly or gradually. More or 

 less intense dyspnea develops in consequence of the displace- 

 ment and collapse of the lung. It often increases gradually and 

 may lead to attacks of suffocation and to a fatal termination, 

 within one-half to one day. Rapid deterioration is particu- 

 larly seen after bilateral pneumothorax or after one due to the 

 breaking through of an abscess or of a gangrenous focus. Slow 

 ingress of air in other cases leads to much less violent symp- 

 toms ; these may, in fact, be so slight that they are overlooked 

 and the pneumothorax is only discovered during a physical ex- 

 amination. 



The shape of the thorax in valvular pneumothorax may be 

 so changed that the diseased half is more prominent, while in 

 other forms the healthy side or both halves may become promi- 

 nent. Tenderness on pressure upon the intercostal spaces points 

 to pleuritis or to fracture of the ribs. 



In valvular pneumothorax, the percussion sound is atympa- 

 nitic, loud, and possibly somewhat weakened, in consequence of 

 increased tension of the chest wall. In open pneumothorax, the 

 sound may be t}T;npanitic in all species of domestic animals, in 

 the presence of a sufficiently large opening in the thorax wall; 

 if, however, pneumothorax is open toward the air passages and 

 if the opening can not be large, a tympanitic sound is only heard 

 in small animals, because in them onlv the small column of air 



