660 SUBCUTANEOUS EMPHYSEMA. 



the flank. Diffuse suppuration may then be set up in these parts, 

 and may extend far bej'ond them. 



In the ox emphysema rarely becomes generalised, but in the sheep 

 and goat extension is more common ; the patients perish of intoxi- 

 cation, caused by reabsorption of septic gases. 



Under other circumstances emphysema may be due to an injury 

 in some region where the connective tissue is loose and pliable, as for 

 instance the region of the elbow, the internal surface of the shoulder, 

 or the fold of the flank. Every time the animals move the tissues 

 are displaced, and air being drawn in, it is imprisoned by the valve- 

 like action of the injured part and gradually finds its way into the 

 subcutaneous tissue. 



Accidental injuries to the trachea, particularly injuries produced by 

 dogs biting sheep or goats, are always accompanied by local emphy- 

 sema, unless the wounds in the skin and trachea correspond, which 

 rarely happens. At every respiration a portion of the air expelled 

 passes into the peritracheal tissue, from which it gradually invades 

 neighbouring parts, and may attain the mediastinum, etc. The 

 injured animal thus inflates its own tissues and dies from asphyxia. 



The open lesions due to pulmonary echinococcosis, and the acci- 

 dents associated with pneumo-thorax, tuberculous caverns and abscesses, 

 or pulmonary emphysema may become points of departure for local, 

 general, interstitial or subcutaneous emphysema. 



The diagnosis of accidental emphysema presents no difficulty, for 

 the local swellings can only be mistaken for those of blackquarter. 

 In the latter disease, however, fever is a constant accompaniment, 

 whilst in simple emphysema it is absent. 



Nevertheless, it is well to remember the possibility of complications 

 due to compression, asphyxia, and even intoxication. 



The prognosis may be very hopeful or very grave. Everything 

 depends on the primary lesion, and it is therefore important that the 

 practitioner should know how to interpret the course of affairs. 



Treatment. In slight cases the best method is to immobilise the 

 parts and await developments, but in grave cases, for instance where 

 the trachea is much injured, the animal should at once be slaughtered. 



Scarification, cutaneous incisions, and massage were formerly 

 recommended as a means of aiding the escape of gas accumulated 

 in the tissues. Such methods, however, are useless, and have the 

 disadvantage of causing numerous suppurating wounds. 



Provided the initial wounds are not seriously infected and the 

 animals are kejDt quiet, in a well-ventilated place, the gas gradually 

 becomes reabsorbed, and healing may take place in a fortnight or 

 three weeks. 



