524 OPERATIONS ON THE CIRCULATORY SYSTEM. 



operations of considerable magnitude, the means of subduing it 

 should always, especially in cases of that class, be included among 

 the customary instruments and appliances of the working surgeon. 

 The flow may proceed from any of the blood vessels, the arteries, 

 however, from the nature of then- functions and the force of their 

 action, requiriag more frequently and more particularly the appli- 

 cation of precautionary and remedial measures. 



Temporary or Preventive Hemostasia. 



This becomes necessary as an occasional expedient, when the 

 presence of the blood is likely to become an obstacle to the opera- 

 tion, and the preventive means may be appHed either before or 

 during its performance. Included under this general head is the 

 circular compression, or ligation en masse, when the situation and 

 the form of the region render it practicable. The effect of this 

 being the flattening or collapse of the vessels, and the temporary 

 closure of their calibre, one of the necessary conditions of its suc- 

 cessful application, especially with the superficial vessels, is that 

 they should be situated near enough to some structure sufiiciently 

 hard and solid to fm-nish an unyielding 2)oiiit appui to the com- 

 pressing agent. If, from the jDOsition of the artery, no such point 

 of resistance can be made available among the surrounding parts, 

 resistance can be established by a double pressure made in op- 

 posite directions, in such a manner that the compressing powers 

 can furnish mutual support, each to the other. By this plan com- 

 pression can be effected in four different ways. 



1st. JBy Digital Pressure. — A^Tien this can be applied and 

 proves sufficient, it is the simplest and the best mode. While it 

 serves to obstruct the cu'culation, its action is limited to the ves- 

 sel which alone needs it, and the tissues are not contused by the 

 pressure; it can, moreover, be suspended or renewed at will, and 

 can be managed by an assistant who may be placed in a position in 

 which interference with the oi:)erator can be entirely obviated, and, 

 indeed, can sometimes be performed by the surgeon himself. It 

 is obtained by pressing the vessel with the tips of the fingers 

 placed either vertically upon the vessel itself, or along its course ; 

 and only such a moderate degree of force need be employed as will 

 prove sufficient to close the calibre of the vessel, without fatiguing 

 the hand by uimecessary pressure. 



