196 OPERATIONS ON THE SKIN AND CELLULAR TISSUE. 



■while lying down has his hind leg extended by the traction made 

 upon it by assistants with a rope. An iacision is made above 

 with the bistoury, and the needle introduced tkrough it, it is 

 pushed downward in front of the joint, carefully raising the skin 

 as it progresses, to avoid injury of the femoro-patellar articulation. 



(ff) Set07i on the Abdomen. — This seton is both difficult and 

 dangerous to apply in the standing position, and, therefore, unless 

 the animal is very carefully secured, and the operator unusually 

 dexterous, it is better to have the animal cast. The seton placed 

 on the median hne, under the abdomen, extends from about the 

 xyphoid cartilage back to near the sheath or other mammae. In 

 applying it, care must be taken to avoid injury to the tunica abdom- 

 inalis and the abdominal muscles, or making a deep wound of 

 the abdomen. Caution must also be exercised against the possi- 

 bihty of the animal kicking against the needle at the moment of 

 its passage thi-ough the skin at the opening of exit. The tape 

 when introduced in the eye of the instrument is to be drawn into 

 the tract by pulling the needle away from behind forward. 



(A) Setons to the JVeck. — -These are recommended against im- 

 mobility and periodic ophthalmia. They are placed in an obUque 

 direction, one or two, on one or both sides of the neck. The hori- 

 zontal direction sometimes recommended is certainly quite un- 

 likely to facilitate the free escape of pus. In introducing the 

 needle it is better to direct it from below upward, starting at 

 about the level of the convexity of the mastoido-humeralis muscle. 



(i) Setons on the Cheeks. — These have been more or less ad- 

 vised in the treatment of diseases of the eyes, and principally of 

 periodic ophthalmia. They are placed a little below the zygomat- 

 ic spine, below and in front of the temporo-maxillary articulation, 

 and extend downward some distance in front of the zygomatic 

 crest. The blood vessels of that region, and principally the large 

 nerves which cover the masseter muscles, must be carefully avoid- 

 ed, to guard against paralysis of the lip. 



(j) Setons in the Foot. — The insertion of a seton in the foot, 

 or the frog-seton, as it is also called, has been principally recom- 

 mended in the treatment of navicular disease, though it is con- 

 sidered by many as of very doubtful utUity. A special curved 

 needle (see Fig. 222) is used for the purpose. The horse is in 

 some instances kept in the standing position, whUe in some special 

 cases it is better to have him thrown. 



