9 March, 1908.] Diseases of Farm Animals. 155 



of the wound, the formation of matter (pus) is encouraged and often pro- 

 ceeds to the extent of abscess formation, or bur"owing into surrounding 

 tissues. If the discharges are of a toxic character they are liable to be 

 absorbed and produce some form of blood poisoning (septicaemia) or, as 

 v.'hen the Tetanus (lockjaw) germ has been introduced, some specific 

 disease. The untoward conditions instanced are more likely to occur when 

 the puncture is in a downward direction because the wound fluids then 

 receive no assistance from gravity in discharging. In such cases it is 

 necessary to enlarge the external wound by a downward stroke of the knife 

 for such a distance and in such a direction as will allow the outflow of anv 

 discharge. Gun-shot or bullet wounds may be classed as punctured wounds 

 and they require the same treatment. 



Lacerated Wounds. — A good example of this type of wound is seen 

 in " broken knees." The edges and surfaces of the wound are torn and 

 bruised, and present a ragged or shredded appearance. Such wounds are 

 most often " dirty '' and almost always result in pus formation. 



The Healing of Wounds. 



Simple clean cut wounds may heal by either of the processes " im- 

 mediate union" or "'primary adhesion." The former occurs when the 

 bleeding is slight and the cut surfaces are brought into exact apposition. 

 The severed ends of the blood vessels unite and the blood flow through 

 tnem is re-established. Minor surface cuts on a man's hand often heal 

 in this way but wounds in the lower animals are seldom, if ever, so healed. 

 In primary adhesion the wound surfaces become gummed over with an 

 exudate of lymph from the small blood vessels of the cut tissues. Ad- 

 hesion of the surfaces is thus produced and maintained until new cells are 

 formed by which permanent union is effected. . This method of healing 

 is also rare in animals. 



The most common method of healing is by the process known as 

 " granulation." In this process there is growth of new tissue called 

 scar tissue which forms bv cell-proliferation and which ultimately becomes 

 organised or permeated with blood vessels and nerves. This scar tissue 

 is at first soft, tender and easily bled and is called granulation tissue. In 

 the case of a gaping wound it gradually fills up the wound from the 

 bottom to the surface level. At times the growth may extend so as to 

 ^tand out beyond the lips of the wound and produce the condition known 

 as " proud flesh." In a wound in which the cut surfaces are oppo.sed to 

 each other the two layers of granulation tissue come together and unite bv 

 mutual pressure and the formation of blood vessels. The new scar tissue 

 on the surface of a healing wound gradually hardens and acts as a false 

 cuticle forming a "scar" or "cicatrix." It is a peculiar property of 

 scar tissue that for a lengthened period it undergoes contraction, and so 

 scars gradually lessen and in the case of small wounds become practically 

 obliterated in time. 



Healing under a scab is perhaps the most salutary method of heal- 

 ing, the scab preventing the introduction of germs, dirt, and other foreign 

 matter and forming a natural protection against cold, wet and other 

 adverse external influences. The scab is formed by the drying of the 

 gummy fluids (lymph) and blood and pus which ooze from the wound 

 surfaces and, except disturbed by violence, it usually remains attached 

 until the citatrix is suflficiently hardened to withstand exposure. 



Treatn]ent of Wouqds. 



The sine qua non in the treatment of all woimds, and especiallv of 

 severe wounds, whether they be incised, punctured, lacerated, or bruised. 



