H.-EMOSTASIS BY TORSION. 



121 



and divided, leaving the artery itself free. If preferred the artery 

 sheath may be torn through, using two pairs of dissecting forceps. 

 The artery is freed from its sheath for some distance as in Fig. 155 

 (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 by means of an aneurysm needle. Care must be 

 taken that only the artery, and not the accompanying vein or nerve, 

 is included in the ligature. One end 

 of the ligature is held 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. 156. The ends of 

 the ligature are then cut off short, 

 and the wound sutured and dressed. 

 After ligation the neighbouring parts 

 are nourished by collateral anasto- 

 mosing branches (Fig. 161). In 

 injuries to large vessels, however, 

 the existence of this collateral cir- 

 culation 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 con- 

 sidered dangerous to ligature veins. 

 Nowadays no distinction is made 

 between veins and arteries. Large 

 veins, however, should be doubly 

 ligatured for similar reasons to 

 those above stated, and also be- 

 cause in the case of large veins 



air might possibly be aspirated through that portion of the vein 

 nearest the heart with fatal consequences. 



Torsion may replace ligation in dealing with small arteries and 

 veins. The mouth of the bleeding vessel is seized with forceps, 

 drawn slightly forward, and the forceps rotated five or six times 

 (limited torsion). To make quite sure of closing the vessel 

 some surgeons continue torsion until the coats rupture (unlimited 



Fig. 161. — Figure'sho wing restoration 

 of blood supply by collateral vessels 

 after ligation of main trunk ; from 

 a preparation of the femoral artery 

 of a large dog eight months after 

 ligation. 



