THE EESPIRATOEY APPARATUS. 3cJl 



puncture into tlie chest. It is pierced by means of a scalpel. 

 The trocar is theninserted through the thoracic wall at about 

 the centre of the lower third_, near the anterior margin of 

 the rib. Directly the wall is punctured the canula is pushed 

 farther in, and the trocar withdrawn (Fig. 64). It is not 

 considered advisable to thoroughly empty the chest, and thus 

 suddenly and completely remove from the lung all the pres- 

 sure exerted by the fluid. Again, a rush inwards of air must 

 not be allowed. If a free flow of fluid does not occur, or 

 suddenly ceases, it may be due to lymph plugging the 

 tube ; this must be removed with a probe. In all cases 

 where empyema is diagnosed this operation must be 

 resorted to. It may require to be repeated two or three 

 times, and cases have been known to recover under this 

 treatment. Prognosis, however, is decidedly unfavorable. 



Pneumothorax is accumulation of gas in the pleural sac, 

 due either to injury of the lung or a wound communicating 

 with the exterior. If the opening be closed the air will be- 

 come absorbed. 



Pleuro-pneumonia sporadica. — We find that frequently 

 pneumonia and pleurisy are concomitant, the disease ori- 

 ginating either in the lungs or the pleura. The symptoms, 

 pathological changes, and methods of treatment which are 

 most beneficial are compounded of those of pleurisy and 

 pneumonitis, and do not here need recapitulation. The 

 case seems most like one of pleurisy in some instances, of 

 pneumonitis in others. The most important question for 

 consideration, with regard to this disorder, is in what 

 respects it is to be distinguished from the epizootic pleuro- 

 pneumonia. This is a matter of much importance, 

 especially to veterinary inspectors. The existence of 

 this sporadic disease has been denied, but most 

 unwarrantably. 



Causes. — It cannot be attributed to contagion, but 

 results from exposure to cold, and other influences liable 

 to generate inflammation of the respiratory organs ; seldom 

 runs through a herd ; several animals, similarly exposed, 

 may become simultaneously affected, but removal of the 

 cause leads to cessation of fresh cases ; is most prevalent in 



