PRINCIPLES OF VETERINARY SURGERY 193 



1st, Natural Haemostasis and 2nd, Artificial Haemostasis. 



I St. NATURAL H^MOSTASIS.— If the blood chan- 

 nel is perforated, even at a dependent part of the body, all of; 

 the blood within will not escape. It will not flow out in obed- 

 ience to the law of gravity as in the case of the liquid con- 

 tents of a perforated barrel. AVhen the breach is confined 

 to capillaries, small veins or small arteries, the outward 

 flow of blood, under normal conditions, is trivial. Only a 

 small quantity will escape. If the breach, on the other 

 hand, is located in a vein or artery of considerable size, the 

 flow may be copious, but ordinarily, not in sufficient quan- 

 tity to cause death. And lastly, if a large vessel, such as 

 the carotid artery or jugular vein, is severed, the flow will 

 cause death, but in spite of the large breach, an abundance,^ 

 of blood will still persist in remaining in the organism. 

 Nature's forces which protect the organism against the loss , 

 of all of its blood from every trivial breach in the continuity 

 of the blood channel, are three in number: — a. The coagu- 

 lability of the blood; b, the contractility of the blood ves-, 

 sels; c, the diminution in the force of the heart beats as the. 

 volume ot blood diminishes. 



a. Coagulability of the Blood. — Blood that is no longer 

 in motion, that comes in contact with foreign matter, or that 

 is exposed to external influences, promptly coagulates. In 

 the bleeding wound it gathers around the severed blood 

 vessels, adheres to the ragged fibers of the wounded tissues 

 and accumulates so as to fill the traumatic cavity, and: 

 thus, more or less effectually, blocks the outward flow, of 

 blood. This force alone is sufficient to arrest the flow of 

 trivial wounds, but it is often subordinate to such external 

 mfluences as motion, friction, etc., and to the character 

 of the tissues in which a wound is located. The wour\d 

 of a large vessel traversing between a bone and the skin. 



