AEREST OF BLEEDINa. 65 



isheath and in front of the cut end by the blood when flowing over the divided 

 surfaces. The comparatively small amount of bleeding which takes place from 

 arteries that are severed by scraping with a jagged knife, is chiefly due to the 

 increased roughness of the divided parts over which the escaping blood passes. 

 When the bleeding has been stopped by this external coagulum, " an internal 

 coagulum " begins to form within the artery at its cut end, by the continued 

 coagulation of blood. If all goes on favourably, the cut surface at the end of 

 the artery, grows together (to use Hamilton's expresf-ion), in exactly the same 

 way as in an ordinary wound, and the artery becomes permanently closed by 

 a scar. '* It must be clearly understood that, according to the views held by 

 modern pathologists, the thrombus (internal coagulum) takes no more share 

 in the production of the fibrous tissue than does the layer of blood-clot which 

 cements together the surfaces of a wound. The thrombus is replaced by 

 fibrous tissue, but not converted into it" [Erichsen). The tendency of the 

 bleeding from an artery to become spontaneously arrested, being proportionate 

 to the comparative quantity ol the muscular fibres in the middle coat, will 

 vary in inverse proportion to the size of the vessel. Practically speaking, 

 this natural method of arresting hoemorrhage would be insufficient to save the 

 animal's life, in the event of division of any of the large arteries. As a rule, 

 an artery which has been cut straight across, will stop bleeding in a shorter 

 time, than if it had been only partly divided ; for in the latter case there will 

 be only slight retraction of the separated parts within the sheath. 



In almost all cases of a cut artery, the end nearest to the heart will be the 

 only one of the two which will require to be closed. The scarlet colour of the 

 blood and the jetting out of that fluid in harmony with the contraction of the 

 left ventricle of the heart, will be characteristic of a wounded artery. 



When an artery is tightly ligatured or twisted, the comparatively brittle 

 internal and middle tunics become ruptured, and their ends retract and turn 

 inwards, so that they offer resistance to the blood flow, and encourage the 

 formation of the internal coagulum ; while the outer coat being strong and 

 tough, gives an effective support to the ligature, or closes the tube by remain- 

 ing twisted on itself, as the case may be. 



Torsion is preferable to ligature even for large arteries ; for it is less apt to 

 interfere with the healing of the wound, especially if the ligature be not of an 

 antiseptic material which can be readily absorbed, and it can be quickly done 

 by one person. The ligature, if used, should be of such a strength that it will 

 not be absorbed before it accomplishes its special duty of keeping the vessel 

 closed. 



Besides the spontaneous arre. t of bleeding by the constriction of the cut 

 end, by its retraction within the sheath, and by the formation of an external 

 and internal coagulum ; the stoppage of hc^morrhage will be greatly aided by 

 the animal becoming faint from loss of blood, in which case the rapidity of 

 the flow will be reduced by the action of the heart becoming weaker, 

 and the tendency of the escaping blood to form a clot will be proportionately 

 increased. 



The application of styptics (oil of turpentine, solution of perchloride of 

 iron, for instance) checks bleeding by causing the blood at the seat of injury to 

 coagulate. Hence, before employing them, all blood and clots should be 

 removed from the wound. 



The hot iron stops bleeding by forming at the end of the artery an eschar 

 or crust, which appears, as a rule, to implicate all three tunics. UsuaFy the 

 hot iron is more effective m stopping haemorrhage when it is at a dull red 

 iieat, than when it is hotter. 



The application of heat or cold through the medium of water, tends to 

 check b.eedmg by causing contraction of the muscular fibres of the middle coat 

 01 tHe arteries. The contractions produced by the employment of hot water (at 

 a temperature of not less that 110° F.) begin quicker, last longer, and are more 

 energetic than those induced by the use of cold water, the continued effect of 

 wliich is to paralyse the tissues.' The application of lukewarm water 

 enc(jurages bleeding. 



5 



