526 OPEEATIONS ON THE CIKCULATORY SYSTEM. 



consists of a roller of India rubber, to be so applied 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 poiat of incision. The pressure pro- 

 duced by this band can be regulated by means of a tourniquet, 

 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 taU, or the removal of 

 tumors. 



Permanent, oe Definite Hemostasia. 



The arrest of hemorrhage may become necessary at any step 

 of an operation, l^ut it is ordinarily when it has been completed 

 that the indication must be fulfilled. 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 capUlary, 

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

 the influence of the retractility 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 circiilatory system ; but serious accidents 

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

 sure upon the orifice wiU. generally insure the formation of a clot 

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

 longitudinally by a lateral incision, pressiu'e at the point of the 

 wound, though not strong enough wholly to stop the circulation 

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

 ation of the wound. But when large veins or arteries are opened, 

 or even when the capillary hemorrhage is usually abundant, more 

 compHcated means of hemostasia must be resorted to, and not 

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

 means of obtaining permanent hemostasia are of two kinds — one 

 taking effect through \he 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 styptics, and piotential and actual cauterization. 



