SETONS. 079 



leave the instrument longer in than a quarter of an hour, so as to 

 avoid, in some measure at least, the chance of peritonitis. Some 

 practitioners take it out after five or six minutes, if the escape 

 of gas has ceased by that time. Another objection against allowing 

 the cannula to remain long in, is that it might wound the intestine 

 during the struggles of the animal, or on the collapsing of the 

 bowel. 



To remove the cannula, we should seize it with the right hand, 

 and should raise it rapidly, but without roughness. 



There is no need to do anything to the external wound; as the 

 puncture becomes closed up by reason of the hole which was made 

 through the skin, shifting its position away from that made through 

 the abdominal muscles, on the swelling going down. 



The practice of injecting medicines through the cannula is 

 dangerous; for the fluid might go the wrong way and escape into 

 the abdominal cavity, with the very probable result of peritonitis 



Fig. 173. — Curved seton needle. 



and death. It is much better, as a inile, to give a drench in the 

 ordinary manner. 



Setons 



are pieces of tape or other suitable material which are passed into 

 various tissues in order to set up irritation in the part, and con- 

 sequently to draw an increased supply of blood for the repair of 

 some neighbouring diseased or injured structure. The best kind 

 is broad white linen tape, or as broad a strip of calico as the 

 needle will take. A seton needle is a large, flat, steel needle made 

 for inserting the t^ape, and may be straight or curved (Fig. 173). 

 Those used about a joint, such as the hock, should have the point 

 blunt, in order to prevent injury to the capsular ligament; but 

 should have the sides sharp. Rowelling scissors should be used 

 to cut through the skin at the points for insertion and exit of the 

 seton needle. A handle, to which the needle may be fixed, is em- 

 ployed to force the point through deep-lying, or hard tissues. When 

 the tape is passed through the part, its ends may be tied together, 

 or knotted separately, an inch or two being left over, and the extra 

 lengths are cut off. The tape, as long as it remains in the part, 

 should be pulled backwards and forwards a little, once or twice 

 every day, so as to keep up a continued state of irritation. The 



