EXTRAVASATION OF GAS. 421 



tomatic of inflammation, and as such must be attended to 

 in common with its cause. In the latter, it usually results 

 from external violence, and comes under the popular term 

 of a bruise, to which the reader is invited to turn. An 

 injury of this kind may so aflect the organization as to 

 render it impossible for the extravasated blood to be re- 

 absorbed ; in which case both the extravasation and disor- 

 ganized parts become involved in one common sphacelus, 

 and either a healthy suppuration and granulation closes the 

 wound, or the constitution sinks under the process, and life 

 is destroyed. In lesser injuries, the extravasated fluid is 

 absorbed ; or, if it remains, it continues as a fully organized 

 hardened tumour, its aqueous portion disappearing. 



EXTRAVASATION OF GAS, OR EMPHYSEMA. 



Emphysema is the escape of gas into the cellular mem- 

 brane, from deep-seated morbid combinations ; therefore 

 it is seen in the pestilential epidemics. Emphysema is 

 also brought on by the entrance of the atmospheric air 

 into a wound, from which it makes its way more or less 

 extensively throughout the cellular tissue. When it happens 

 within the cavity of a joint, it often confines itself to that 

 only : but in other, and fortunately very rare, cases, it per- 

 meates through the whole cellular surface, from the head to 

 the tail, rendering the unfortunate animal one bloated mass, 

 wdiich soon destroys him by its irritation, unless he be killed 

 by shorter means. It was formerly a custom to make a 

 slight puncture into the integuments of the elbow or arm, 

 and by means of a quill to blow a quantity of air into it 

 until the whole shoulder became distended, as a cure for a 

 shoulder strain. It is also still a custom to make veal em- 

 physematous, by blowing air from the mouth of a butcher 

 into any point of the carcass of the dead calf; which plumps 

 up the cellular tissue, and takes ofl" that flaccidity common 

 to the young animal. The most common origin of emphy- 

 sema, however, arises from lesion of the aerating organs, as 

 wounds of the trachea, bronchia, or substance of the lungs : 

 a broken rib, by being forced inwards and puncturing the 

 pleura, is a common cause. The presence of air within the 

 cellular membrane is always a source of irritation : when, 

 therefore, it is very extensively diftused, it may so irritate 



