PNEUMO-THORAX. 365 



pneumo-thorax, is suggested by progressive improvement in the symp- 

 toms. Scientifically it is very easy to make this diagnosis by putting a 

 manometric apparatus in communication with the pleural cavity by means 

 of a simple hollow needle provided with a thick-walled rubber tube. 



In open pneumo-thorax the liquid column in the manometer under- 

 goes rhythmic oscillations corresponding to the respiratory movements ; 

 in valvular pneumo-thorax the intra-pleural pressure increases progres- 

 sively until it becomes higher than the external pressure ; and finally, 

 in closed pneumo-thorax, the column of the manometer assumes a cer- 

 tain level at which it rests. 



Prognosis. The prognosis is very variable, according to the primary 

 cause of the accident. Animals might recover, but economically there 

 is little advantage in preserving them when the diagnosis is assured, 

 except in cases of animals of great value, and when the primary disease 

 admits of it. 



Causation. Pneumo-thorax may be produced by various causes. 

 The most frequent cause in large animals is pulmonary echinococcosis, 

 during the course of which a peripulmonary vesicle, after having injured 

 several lobules, one of the air passages or even a bronchiole, may break 

 through the pleura, thereby setting up direct communication between 

 the bronchi and the pleural cavity. 



To pulmonary tuberculosis, with peripheral softened tubercles, 

 perforating simultaneously into an alveolus or a small bronchus and 

 iiito the pleura, must be assigned the second place. 



Vesicular and interstitial sub-pleural pulmonary emphysema is also 

 a frequent cause of pneumo-thorax, the pleura being ruptured over the 

 emphysematous points. 



Finally, and exceptionally, an abscess of the lung may open into the 

 pleura and form sinuses, which may establish a communication between 

 the digestive reservoirs and pleural-sacs ; but such accidents produce 

 pyo-pneumo-thorax and septic pleurisy of a rapidly fatal character. 



The diagnosis of pneumo-thorax, and even of its varieties, does not, 

 however, enable one to form a prognosis ; the important point is to 

 ascertain the original cause. 



Treatment. It may be said of pneumo-thorax that no treatment 

 exists, and that the position is one of expectancy. In fact, we possess 

 no means of directly dealing with such diseases as echinococcosis, tuber- 

 culosis, or emphysema. For this reason it is best as a rule to advise 

 slaughter. Nevertheless, when the condition is due simply to pulmonary 

 echinococcosis of a discrete character, there is some chance that after 

 several months the animal may recover spontaneously. The communi- 

 cating orifice becomes closed by reparative processes (cicatricial contrac- 

 tion, the formation of a false membrane, limited adhesion between the 



