Hi4 LINEAR FIRING. 



released and carried either backward or forward. When the pastern 

 or coronet is to be fired, the two limbs can be fastened together above 

 the knee or hock respectively, the diseased limb being released from 

 the hobble and drawn forward or backward by an assistant using a 

 broad strip of webbing. 



In line firing, the important point is to trace equally spaced 

 straight lines, extending beyond the diseased region. Converging 

 lines should never cross or unite, the points of crossing being very 

 liable to slough (see Fig. 218). The spaces between the lines vary 

 according to the thickness of the skin and the extent of the cauterised 

 region. Closely placed superficial lines are preferable to others 

 more distant and more deeply penetrating. As a rule a space from 

 three eighths to three fourths of an inch should divide the lines. In 

 France the custom is first to lightly mark out the design, and after- 

 wards to pass the cautery over the lines a number of times. The 

 iron is used at a dull or bright red, the latter being the maximum 

 temperature allowed, and is passed slowly along 

 v \ ^ the marked-out design without pressure, the 



\ . ^ blade being always kept perpendicular to 



s \. ^ the surface. The iron should never be passed 



"\ ^ twice in immediate succession along the same 



line, and if the French method be adopted, 



Fig. 218.— Pattern for ^ e \j nes must be retraced in regular order, 

 line firing. The lines .. . , , . 



do not meet. otherwise sloughing is apt to occur. 



The operator judges when the cauterising 

 action is sufficient by the appearance of the base of the lines, the ex- 

 udation which has occurred, the infiltration of the skin, and the degree 

 of separation shown by the epidermis. Judged by these standards, 

 three degrees of cauterisation may be distinguished. In the first the 

 lines are shallow and contain a few little drops of serosity. Their base 

 is of a golden yellow, the skin is little infiltrated, and the epidermis is 

 still adherent. In the second the lines are deeper, their base yellowish 

 brown, exudation is more marked, and the epidermis is loosened. 

 In the third the epidermis is almost cut through, the margins of the 

 lines tend to gape and produce irregular edges, the serous dis- 

 charge from their base is abundant, and the skin is often covered 

 with vesicles. In the French system the iron is heated to a cherry 

 red, and is passed along each line five or six times in light firing, 

 eight to ten in ordinary firing, and twelve to fifteen in severe firing. 

 It is clear, however, that the number of passages must vary with 

 the weight and temperature of the cautery, the judgment of the 

 operator, and the thickness of the skin. 



