570 



GUIDES IN riTNCTURTNO THE BOWEL. 



The precise cause of the greater vulnerability of the peritoneum in 

 horses is still unknown, though it is clear that peritonitis is only caused 

 by infective materials introduced through a wound, or derived from 

 the intestine. The operator must endeavour to prevent such in- 

 fection ; but though it is easy to guard against soiling from without, 

 it is impossible to prevent it from within, i.e., from the bowel itself 

 at the moment of withdrawal of the cannula. To minimise risk, 

 the instrument must be of small calibre, as small, 

 indeed, as will allow of free escape of gas. The 

 trocar should be 9 or 10 inches long, and not more 

 than | inch in diameter. Friedberger's model has 

 met with wide approval (Fig. 409). Cannulae with 

 side openings are to be avoided on account of their 

 favouring infection of the peritoneum. 



The seat of operation is in the right flank, over 

 the arch of the caecum and fourth portion of the 

 double colon, which in tympanites are closely applied 

 to the abdominal wall. The lower portions of the 

 colon usually contain masses of ingesta, while the 

 gases collect . in the upper parts, whence their dis- 

 charge by means of the cannula is both easier and 

 Sless dangerous. The field of operation, which is fairly 

 extensive, is bounded above by the transverse pro- 

 cesses of the lumbar vertebras, in front by the posterior 

 edge of the last rib, behind by the angle of the haunch, 

 and below by a line drawn from the middle of the last 

 rib. The point to select is that which projects most 

 prominently and returns a tympanitic sound on per- 

 cussion, but should these signs for any reason be 

 wanting, or appear more distinctly at another spot, 

 the latter may be selected without disadvantage. 



The trocar and cannula should be boiled for five 

 to ten minutes in soda solution, the hair clipped or 

 shaved off, the skin washed with soap and rinsed with a disinfectant 

 such as iodine, or sublimate solution. 



The trocar is then thrust through the abdominal wall at the point 

 indicated. To render its passage easier, an incision may first be 

 made through the skin with a bistoury, though this is seldom 

 necessary. In passing the instrument it is steadily pushed down- 

 wards and inwards or slightly towards the left side of the horse. 

 As a rule, the trocar can be introduced for 4 to 6 inches, or even to 

 the flange of the cannula without danger. The stilette being with- 



Fig. 409. 

 Friedberger's in- 

 testinal trocar 

 for horses. 



