456 BUREAU OF ANIMAL INDUSTRY. 



or white of egg. If the irritant has been caustic potash, soda or 

 ammonia, vinegar should be the first application. If sores result they 

 may be treated like ordinar}- wounds. 



WOUNDS OF THE SKIN. 



These are divided into incised {clean cut) wounds, lacerated (tot^n) 

 wounds, and contused (bruised) and 'punctured wounds. 



Incised wounds are the simplest, and the sharper the instrument and 

 the cleaner the cut, the greater the hope of spccd}^ healing. Some- 

 thing, however, depends on the seat and direction of the wound; thus 

 one running from before backward on the bod}^, or from above down- 

 ward in the limb, will not tend to be drawn open and gape as would 

 one running transversely on the body or liml). Again a wound on a 

 joint and running across the limb will gape when the joint is bent. 

 Again, a clean-cut wound which has not been exposed to the air, and 

 which lodges no foreign bod}' and no septic nor infecting germ, will 

 heal readily by simple adhesion, whereas those that have been exposed 

 and contain matter foreign to the tissues will have healing delayed or 

 prevented hj the disturbing action of such bodies. 



Healing in wounds may be said to take place by these modes: 



(1) By primary adhesion., in which case the spherical {embryonic) 

 cells, and the stellate connective tissue cells thrown out on the surface 

 of the wound, rapidly multiply and form a bond of union between the 

 divided lips. Union by this means may be affected within twenty- 

 four hours after the wound has been inflicted. Of all domestic ani- 

 mals, however, the horse is the least prone to such union, being more 

 disposed to the formation of pus. 



(2) B}' (jramdation., which is the common form of healing in raw, 

 exposed sores, in those containing foreign bodies and septic and 

 infecting ferments; also in torn and contused wounds. In this form 

 the wound becomes covered with a layer of embr3'onic cells, of which 

 the superficial ones degenerate into pus cells, and thus the surface is 

 kept moist by a layer of whitish, cream}' pus. In the deeper layer of 

 cells minute loops of capillary blood vessels start up, causing the small 

 rounded elevations known as granulations. In this way the deeper 

 layer of cells receiving a blood supply is transformed into connective 

 tissue, and from its surface new loops of blood vessels start into the 

 layer above, and thus layer after layer of new tissue is formed, and 

 the breach caused by the wound is gradually filled up. The new tis- 

 sue as formed undergoes a steady contraction, drawing in the adjacent 

 skin over the wound, and hence large wounds healed in this way have 

 the skin more or less puckered around them. 



(3) By secondary adhesion., in which two granulating lips of a 

 wound having been brought together and kept in apposition, union 

 takes place through the medium of the cells, as in primary adhesion. 



