PRINCIPLES OF VETERINARY SURGERY 195 



of the blood, is the essential protective which prevents death 

 from haemorrhages. 



c. Diminution in the Force of the Heart Beats comes 

 into evidence as a protective influence only as a last resort. 

 It is only active after a large amount of blood has escaped. 

 The heart, weakened from the loss of blood, and through 

 the diminution in the volume of blood essential to stimulate 

 its contractions, no longer drives the current so forcibly 

 through the open blood vessels, E^nd thus arrests the flow, 

 either from sheer lack of force or from permitting the coagu- 

 lum to organize in the traumatic cavity. 



These three mechanisms may always be depended upon 

 to act in behalf of the organism^ in a precise, uniform and 

 effectual manner when the trauma is located in a normal 

 tissue and when the blood vessels are not affected with de- 

 generative changes. The vessels of a diseased structure 

 often, in fact, generally, share in the morbid process and 

 may, as a consequence of their altered anatomical and phy- 

 siological constitution, fail in the essential behavior to block 

 the flow of their blood currents. Certain diseases of the 

 arteries themselves, either general or local, may likewise de- 

 prive them of their protective properties. Diseases of the 

 blood, by diminishing its coagulability, may also serve to aug- 

 ment and perpetuate a haemorrhage that would have been 

 trivial under normal conditions. And finally certain indi- 

 viduals, from entirely obscure causes, are more prone to 

 bleed profusely than others. This latter fact is manifest in 

 many surgical operations upon animals. 



2nd. ARTIFICIAL HEMOSTASIS.— The artificial ar- 

 rest of haemorrhage is accomplished by. different processes 

 which must vary according to the gravity of the haemorrhage 

 and the location of the trauma. 



1st. By Direct Compression. — Direct compression is 

 probably the most common recourse in veterinary surgery. 



