538 OPERATIONS ON THE CIRCTTLATORY SYSTEM. 



Tlie presence of the Kgature and its effect on the surroundings 

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

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

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

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

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

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

 ishing in size, at length disajopears. 



As the resorj)tion of the clot takes place the walls of the ves- 

 sel contract until at length the caHber of the artery becomes en- 

 tii'ely obliterated, and the former tubular canal is transformed into 

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

 nearest collateral vessel. 



This obliterating 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 exist- 

 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 imjoerfect, and in the 

 second, because no clot has been formed. 



(C) Torsion. — This hemostatic j^rocess has been known 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 j)roved 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 aj^plying torsion. Among the 

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

 two ordinary anatomical, another whose branches are terminated 

 by smooth cylindrical jaws, and the fourth the artery-ttiyisting 

 force2)s. The artery is held with one of the ordinary forceps ; 

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

 then the twisting forceps grasp the artery at its extremity in 

 place of the one first used, keei^ing 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 



