WOUND HEALING 127 



only, and the destructive influence ceases immediately 

 upon removal of the cause, whereas the influence of 

 thermic, and especially chemic, causes continues for a 

 variable period. 



Many methods of wound healing have been described, 

 such as immediate union, primary union, secondary 

 union, tertiary union or intention, healing under a scab, 

 and so on. When the exact conditions are understood, 

 it is found that practically all wound healing is of one 

 or the other of two types, primary union or first inten- 

 tion, and healing by secondary union or granulation. 



The process of healing by primary union embraces 

 coagulation of the hemorrhagic extravasate, agglutination 

 of the wound margins, hyperemia, inflammation, vas- 

 cularization, fibrous formation, disintegration of the 

 hemorrhagic extravasate and inflammatory exudate, 

 cicatrization, epithelization, and substitution, the time 

 required for the latter being, much greater than the 

 former. 



The other type of healing — that is, by granulation — 

 is the type usually observed in the majority of wounds 

 in the domestic animals. It is this type in which there 

 is a continued infection and a continual destruction of 

 the newly generated tissue, thus necessarily increasing 

 the length of time required for the wound gap to be 

 filled with new tissue. This type of wound healing can 

 be obtained by any one and under any conditions sur- 

 rounding it. It is certainly no credit to a veterinarian 

 to have under his care several cases of wound healing in 

 which the method of healing is by granulation. 



Prevailing Methods Deplorable 



Healing by primary union is desirable in all wounds. 

 Unfortunately, this method of wound healing is not ob- 

 tained as frequently as it should be in veterinary practice. 



