i68 



OPERATIVE TECHNIQUE. 



distinction is made between veins and arteries. Large veins, however, 

 should be doubly ligatured for similar reasons to those above stated, 

 and also because 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 on their axis. To make quite sure of 



obliterating the vessel some surgeons 

 continue torsion until the coats 

 rupture (unlimited torsion). As in 

 ligation, the middle and internal 

 coats are ruptured, and become in- 

 duplicated ; the external coat being 

 stretched and twisted forms a kind 

 of cap, which covers the clot, and 

 gives it much greater firmness. 

 Ligation, however, is always more 

 certain than torsion. In arterioles 

 of considerable size, moreover, the 

 fibrous coat may untwist, giving rise 

 to secondary haemorrhage. 



Forcipressure by means of arter\' 

 forceps has largely replaced other 

 means of checking bleeding. It 

 consists in appl}'ing to the mouths of 

 divided vessels special forceps (Wells' 

 form is the best), which are left in 



Fig. I95.-Figure showing restoration of POsition for a varying time, some- 

 blood-supply by collateral vessels after times Until the vcsscls are blocked 



ligation of main trunk; from a pre- , , . i .-i i- 



paration of the femoral artery of a ^y clot, SOmetmieS Only Until llga- 



large dog eight months after ligation, ^ures can be applied. If during 

 operation a small artery is divided forceps are immediately applied. 

 By using a number incisions may be made through very vascular 

 tissues with little interruption or loss of blood. To keep the operative 

 field clear they are held to one side by an assistant. It is not 

 necessary that all should be left in position until the end of the 

 operation ; arteries of very small dimensions, if compressed for a few 

 minutes, no longer bleed when the forceps are removed. Should a 

 large vessel be divided, it can be grasped and closed with Wells' 



