64 W0UND8 AND BKUISES. 



liave already indicated, they not only injuriously affect the wound ; but may 

 also cause serious if not fatal damage to the animal's general health. 



ANTISEPTIC TREATMENT OF WOUNDS.— In order to check the 

 injurious action of bacteria, we apply to wounds certain agents called anti- 

 septics, some o>f which, like iodoform, nullify the action of bacteria ; and 

 others, like carbolic acid, destroy them. In a surgical operation which 

 necessitates the use of the knife, we employ an antiseptic to disinfect the 

 parts about the wound, as well as the wound itself, unless we are certain that 

 the wound is absolutely free from putrefactive germs, which are readily 

 carried to it by the knife, ordinary water, our hands, etc. In applying an 

 antiseptic, we must be careful that it is not so strong as to injure the divided 

 tissues. 



" Asepsis is the employment of means and substances absolutely free from 

 infective agents. For example, water which has been boiled and which has 

 thus become aseptic, can be used for washing wounds. 



" All antiseptics have, more or less, an injurious action on the tissues, as 

 well as on microbes, and therefore they diminish the power of resistance 

 possessed by the part. Aseptic surgery, which is based on the employment 

 of aseptic agents that have no injurious action on the tissues, has been in- 

 vented, in order to avoid this drawback. Theoretically it is perfect ; but in 

 practice, the only true way to obtain asepsis, is to use antiseptics " {Cagny 

 and Gohert). 



From the foregoing considerations we may draw the following con- 

 clusions : — 



1. That the fact of a wound of moderate size and untainted with dirt, 

 remaining exposed to the atmosphere for even an hour or so, need not pre- 

 clude the hope of getting it to heal without pus being formed. 



2. That even if we cannot exclude bacteria from a wound, the more we hold 

 them in check (by the observance of cleanliness and by the ui-e of suitable 

 antiseptics), the quicker will the wound heal, and the less risk will the animal 

 run, of becoming inoculated by disease germs. 



3. In the treatment of a wound which is free from bacteria (like those 

 inflicted during an operation that has been carried out under strict conditions 

 of cleanliness), we should, if possible, apply a dry dressing in j)reference to a 

 wet one, for water favours suppuration (the formation of pus), which is the 

 great hindrance to rey)air in a wound. If, however, bacteria have gained 

 an entrance into a wound (as would be the case in broken knees and ordinary 

 cuts, especially if they have become contaminated by dirt, we should freely 

 wash the parts with some antiseptic solution (such as one of carbolic acid or 

 creolin, page 67), so as to check the action of any bacteria that may be present. 



ARREST OF BLEEDING.— Arteries are tubes which consist of three 

 (internal, middle and external) coats or tunics. The internal coat closely 

 resembles a serous membrane (the smooth membrane which covers the lungs or 

 liver, for instance). The middle coat is formed of yellow elastic fibres, 

 and of muscular fibres ; the former predominating in the large arteries ; the 

 latter in the small ones. Hence, the larger the artery, the greater tendency 

 it has to remain open when cut across. In the dead subject, we may recognise 

 the presence of large arteries by the fact that their divided ends gape, and that 

 they are empty. The external coat is composed principally of connective 

 tissue, and is, consequently, much the strongest of the three. Veins are of 

 similar structure to arteries, except that their tunics are much thinner and 

 weaker. 



If an artery is cut in two, the consequent irritation causes the muscular 

 fibres of the middle coat to contract and thus to draw the ends of the artery 

 into its sheath, and also to diminish the calibre of the tube, especially at its 

 divided extremities. Owing to the fact that the passage of blood over rough 

 surfaces increases its coagulability (p. 12), a coagulum is formed within the 



