64 PRINCIPLES OF VETERINARY SURGERY 



a serious injury had been inflicted. In this disease the 

 trauma is usually a simple flexion crevice or trivial abrasion of 

 the skin that admits micro-organisms into the subcutaneous 

 connective tissue. Operative gangrene occurs from various 

 causes after veterinary operations. The ligation of a large 

 artery or even a large vein is, however, the most common 

 cause. Whenever such recourses are necessary in a surgical 

 operation or in the treatment of an accidental w^ound the 

 area supplied by the ligated vessels often becomes the seat 

 of an extensive gangrene. Pressure gangrene, or pressure 

 necrosis, as it is often conveniently called, is also a common 

 form of the disease. This form is caused from the application 

 of taut bandages (bandage necrosis) ; from the suturing of 

 wounds (stitch necrosis) ; from prolonged decumbency (de- 

 cubitus) ; from pressure of the harness, saddle or collar 

 (sit-fast) ; from pulling heavily upon the bit (bit gnathitis) ; 

 or from any severe but especially prolonged pressure upon 

 any given part of the body. An example of pressure gan- 

 grene is seen in strangulated hernia, when the constricted 

 hernial orifice compressed the incarcerated bowel. In all 

 of these cases the primary injury is followed by the invasion 

 of pathogenic microbes which provoke intense inflammatory 

 action and thus become largely instrumental in determining 

 the seriousness of the condition. They always cause the 

 putrefaction which the dead tissues undergo, and without 

 them the gangrene is always subordinate to the force of the 

 initial injury. The so-called aseptic inflammations, simple 

 inflammations, or non-microbian inflammations which in 

 reality are no more than pure physiological regenerations, 

 are incapable of producing a gangrene beyond the area 

 actually killed at the initial blow. All spreading gangrenes 

 of the primary, traumatic types are microbian. That is to say 

 if the prick of a nail or the kick of a shoe results in the 

 sloughing of a considerable area, it is the invasion of micro- 



