538 OPERATIONS ON THE CIBCULATOBY SYSTEM. 



The presence of the Hgature and its effect on the surroundings 

 of the blood vessel give rise to a process of elimination, by which, 

 after a certain time, the Ugatiag thread is expelled, carrying with 

 it the vascular stump situated beyond the ligature. At the same 

 time, and while these phenomena are taking place outwardly, the 

 clot, adhering more and more to the vascular surfaces, soon be- 

 comes the seat of peculiar absorbent changes, and gradually dimin- 

 ishing in size, at length disappears. 



As the resorption of the clot takes place the walls of the ves- 

 sel contract untU at length the caUber of the artery becomes en- 

 tirely obliterated, and the former tubular canal is transformed into 

 a fibrous cord, extending from the point of the Hgature to the 

 nearest collateral vessel. 



This obUteratiag process of the arterial canal may, however, 

 be defeated by the interference of too active an inflammation, pro- 

 ducing the premature sloughing of the ligature, or by the exists 

 ence in too close proximity to the point of ligation of a collateral 

 arterial branch. In both cases hemorrhages may follow ; in the 

 first, because the adhesion of the clot is imperfect, and in the 

 second, because no clot has been formed. 



(C) Torsion. — This hemostatic process has beenknown from an 

 early date, but was not methodically described until about forty 

 or fifty years ago, by Amussat, who recommended it in preference 

 to the method of ligation. But daily experience has demonstrated 

 its inferiority, and proved it to be a less powerful hemostatic meas- 

 ure than that of the hgature, and, moreover, that it is only avail- 

 able for hemorrhages occurring in small vessels. 



There are several ways of applying torsion. Among the 

 principal is that recognized by Amussat. It requires four forceps, 

 two ordinary anatomical, another whose branches are terminated 

 by smooth cyhndrical jaws, and the fourth the artery-twisting 

 forceps. The artery is held with one of the ordinary forceps ; 

 with the other the tissues surroiuiding it are separated from it ; 

 then the twisting forceps grasp the artery at its extremity in 

 place of the one first used, keeping it out of the wound, and when 

 thus secured the instrument with the smooth transverse jaws is 

 applied above it, close to the tissues, and firmly pressed upon the 

 coats of the artery. In this position, the twisting forceps is given 

 a rotary motion upon its axis, as if the vessel were to be rolled 

 over its extremities, and is twisted upon itself by seven or eight 



