184 VETERINARY PATHOLOGY. 



tubercular centers are not wounds. A bruise may or may not 

 be a wound, depending upon the nature of the lesion, i. e.. 

 whether or not the interruption of tissue has been affected. 



Wounds may be classified as tc cause, location, character, and 

 conditio)!. 



1. Etiologicallv wounds may be traumatic, t'~erniic or 

 chemic. 



2. According to location wounds may be, surface or subsur- 

 face, abdominal, cervical, thoracic, etc. 



3. As to their cliaracter, wounds may be incised, punctured, 

 lacerated, contused, stab, shot, or bullet and from bites. 



4. AA'ounds may be noninfectious and infectious. 



Traumatic wounds usually heal more readily than wounds re- 

 sulting from thermic or chemic causes because traumatisms are 

 caused by mechanical force only and the destructive influence 

 ceases immediately upon removal of the cause ; whereas the in- 

 fluence of thermic and especially chemic causes are more lasting 

 as their action continues after the wound has been produced. 



Wound healing may be of one of two types, healing by pri- 

 mary union (first intention), and healing by granulation (sec- 

 ond intention or secondary union). These two modes of heal- 

 ing diiTer only in extent. Other methods of healing have been 

 described as immediate union, healing by third intention, and 

 healing vmder a scab. Inuiiediate union, signifies union of parts 

 of a cell or the cut ends of fibres, etc., and is now thought to be 

 impossible : healing under a seal) and healing by third intention 

 are properly discussed under the caption of primary union or 

 granuation. 



Healinq h\ Priiiiiirv Union. — This is the most desirable 

 method of wound healing and is usually obtained in veterinary 

 practice only in surgical wounds and recently inflicted, clean cut 

 wounds. This mode of healing is of short duration and is ac- 

 companied by little if any infection and limited inflammation. 

 Healing bv primary imion takes place only in clean cut wounds, 

 i. e.. when the tissues are smoothly and evenly divided and in 

 which hemorrhage is limited and easily controlled. After hem- 

 orrhage ceases or has been arrested the extravasate coagulates 

 thus agglutinating and drawing the wound margins together. 

 If the incised surfaces or severed tissues be approximated by 

 surgical procedure the coagulated extravasate and exudate as- 

 sists in maintaining them in that position. In surface wounds 

 varying quantities of serum and lymph discharge and coagulate 

 upon the surface thus forming a scab. The injury producing 

 the wound and the extravasate are sufficiently irritating to es- 



