SETONINU. 



L69 



of chronic lameness and some other conditions, a diagram is furnished 

 below showing the various positions in which setons may be 

 introduced. Setons are inserted with a special needle (Fig. 220), 

 from eight to sixteen inches in length, and usually made of steel 

 or soft iron. The point, sharp or blunt, is spatulate and of steel, 

 the body is usually flattened and often divided into two parts, which 

 can be screwed together. The eye is sometimes at one end, some- 

 times at the other. For the purpose of passing frog setons Sewell 

 invented a special needle (Fig. 220a). For operating on hsematomata, 

 etc., the needle shown in Fig. 220b is used. It consists of two 

 cylindrical portions (about three sixteenths of an inch in thickness), 



Fkj. 219. -Schema showing positions in which setons may be inserted. 



which can be screwed together. The point resembles a three-sided 

 pyramid. 



Should the animal prove very troublesome it may require to be 

 cast before a seton can be inserted, but as a rule it is sufficient to 

 apply a twitch and lift one of the fore-feet. Generally, it is best to 

 pass the needle from below upwards, as should the animal struggle 

 it is more easily withdrawn, while it is less likely to go astray. 

 Should it be inserted in the opposite direction and an error be made 

 necessitating change of direction, a pocket is left in which pus may 

 accumulate. 



Views differ as to the depth to which setons should be inserted. 

 Some prefer the subcutaneous tissue, others penetrate beneath the 

 panniculus. The latter method, however, is sometimes followed by 



