LIGATION OF ARTERIES. 



167 



and its surfaces are brought into close apposition one with another. 

 When using- catgut the ends of the knot may be cut short, but in the 

 case of silk only one is cut short, the other being brought outside the 

 wound unless asepsis be assured. It is withdrawn a day or two later, 

 when the vessel has been cut through. Wells or Greig-Smith's 

 forceps, with large jaws of conical or cylindro-conical section, are very 

 convenient when ligating vessels. The ligature, on being tightened, 

 slips over the nose of the forceps, and surrounds the vessel. Immediate 

 ligation is always to be preferred. Where it is impracticable, as when 

 the ends of the vessels have retracted deeply within the tissues and 

 cannot be discovered, or when the tissues are very friable and break 

 away as grasped, mediate ligation, or ligation in p,G. 193. fig. 194. 

 the continuity of the vessel, may be performed. 



The instruments required are a scalpel, two 

 retractors, dissecting forceps, a director, ligatures, 

 and aneur3'sm needle (Figs. 193 and 194), i.e. 

 a curved needle with fixed handle. The method 

 is as follows : — The skin is incised directly over the 

 artery, the lips of the wound are drawn apart with 

 retractors, and dissection cautiously continued 

 until the arter}- appears. A fold of the artery sheath 

 is then lifted and divided, leaving the artery itself 

 free. If preferred the artery sheath may be torn 

 through, using two pairs of dissecting forceps. 

 The arter}' is freed from its sheath for some 

 distance (Fig. 189), which is semi-schematic. One 

 margin of the sheath is lifted with forceps and 

 drawn slightly away from the artery, around which 

 the ligature is passed b}- means of an aneurysm 

 needle. Care must be taken that only the artery, 

 and not the accompanying vein or nerve, is in- 

 cluded in the ligature. One end of the ligature is held fast with the 

 fingers or forceps and the needle drawn back, leaving the thread around 

 the vessel. The knot is tied in the manner before indicated, and shown 

 in the semi-schematic illustration, Fig. 190. The ends of the ligature 

 are then cut off short, and the wound sutured and dressed. After liga- 

 tion the neighbouring parts are nourished by collateral anastomosing 

 branches (Fig. 195). In injuries of large vessels, however, the existence 

 of this collateral circulation is sometimes responsible for secondary 

 bleeding from the peripheral ends should the vessel not have been 

 ligatured both in front of and behind the injured spot. In former 

 times it was considered dangerous to ligature veins. Nowada3'S no 



Figs. 193, 194. — Aneu- 

 rysm needles. 



