PNEUMO-THORAX. 



363 



As soon as the rupture occurs air passes from the lung into the pleural 

 cavity, and the lung collapses in consequence of the resilience of its 

 elastic constituents. 



Under other, much rarer, circumstances pneumothorax occurs in con- 

 sequence of gas generated in the digestive tract passing into the pleural 

 spaces. The condition then makes rapid progress, and death occurs in a 

 few days. 



Symptoms. The symptoms are well defined. As soon as the acci- 

 dent occurs the animal exhibits extremely marked and sudden dyspnoea, 

 accompanied by heaving at the flank or 

 general agitation of all the muscles of 

 the body. One of the lungs, in fact, has 

 suddenly been called on to perform the 

 functions of both, and at first it natu- 

 rally has great difficulty in meeting this 

 demand. 



The heaving at the flank and the 

 general agitation of the body muscles is 

 due to the fact that the regularity and 

 rhythm of contraction of the diaphragm 

 are disturbed, and the mechanical condi- 

 tions have become different on the two 

 sides. From the first, respiration is 

 moaning and expiration becomes rapid, 

 stertorous and deep, while the face is 

 anxious-looking, and the nostrils are di- 

 lated as though the animal was on the 

 point of suffocation. On examining the 

 animal from in front or behind, the thorax 

 is easily seen to be wanting in symmetry, 

 the side on which the pneumo-thorax 



has occurred being immobile as compared with the sound side. The 

 latter, moreover, is dilated in order to compensate for the loss of function 

 of the collapsed lung. 



Percussion reveals greatly increased resonance on the side of the 

 pneumo-thorax. On the other hand, the opposite side yields a normal 

 sound. 



Auscultation reveals an increase of the respiratory murmur on the 

 side which is still acting and, on the contrary, complete and total sup- 

 pression of the respiratory murmur on the affected side. On applying 

 the ear to the chest wall, a large soft, amphoric souffle of well-marked 

 metallic character is heard. This is particularly clear on respiration, 

 giving the impression of the existence of a large cavity beneath the ear. 



Fig. 171. — Schema illustrating open 

 pneumo-thorax. Right lung col- 

 lapsed; pericardium and heart 

 displaced towards the right. 



