526 OPEKATIONS ON THE CIRCULATORY SYSTEM. 



consists of a roller of India rubber, to be so aj)plied around the 

 seat of the operation as to cause the blood to recede toward the 

 center of the body, its return being prevented by firmly placing- 

 a ligature just above the point of incision. The pressure pro- 

 duced by this band can be regulated by means of a toiu-niquet, 

 or a piece of elastic tubing, or an ordinary string that may be 

 twisted with a stick. This mode of compression is adapted to 

 cases of amputation of the limbs and of the tail, or the removal of 

 tumors. 



Permanent, or Definite Hemostasia. 



The arrest of hemorrhage may become necessary at any step 

 of an operation, Lut it is ordinarily when it has been completed 

 that the indication must be fiilfiUed. It is true that in many in- 

 stances, even after extensive lesions, the hemorrhage will cease 

 spontaneously, but it is equally true that at other times special 

 interference becomes a necessity. If the hemorrhage is capillary, 

 the surgeon may safely overlook it, and leave it to subside under 

 the influence of the retractihty of the tissues ; but if it is of ve- 

 nous origin, it cannot be safely left to spontaneous action. Still, 

 usually it is only when one of the larger veins is the seat of the 

 bleeding that danger becomes imminent, as with those situated 

 near the center of the cu'ctdatory system ; but serious accidents 

 are seldom to be feared. If the vein is cut across, moderate pres- 

 sure upon the orifice will generally insure the formation of a clot 

 which will constitute a sufficient plug, or if the vera is opened 

 longitudinally by a lateral incision, pressure at the point of the 

 wound, though not strong enough wholly to stop the circulation 

 within the vessel, may still be sufficient to assure the rapid obliter- 

 ation of the wound. But when large veins or arteries are oj^ened, 

 or even when the capillary hemorrhage is usually abundant, more 

 complicated means of hemostasia must be resorted to, and not 

 only applied carefully and securely, but also with celerity. The 

 means of obtaining permanent hemostasia are of two kinds — one 

 taking effect through ihe physico-chemical action of special agents, 

 the other including those which are known as surgical means 

 proper. 



Physico-Chemical Hemostatics. 



Among these must be considered the refrigerants, absorbents^ 

 astringents or stgj^tics, and 2>otential and actual cauterization. 



