PRINCIPLES OF VETERINARY SURGERY 191 



dark blood of venous, and the scarlet red blood of arterial 

 hsemorrhag-e. The flow is trivial, constant, oozing and 

 comes from all parts of the trauma. It is relatively short 

 in duration in a strictly normal tissue. It is only in forma- 

 tive tissue, in neoplasms or in degenerated areas that 

 capillary haemorrhage persists for more than a few minutes. 



RESULTS OF HffiMORRHAGE.-^The seriousness 

 of haemorrhage varies chiefly according to the amount of 

 blood lost, although it cannot be denied that sudden loss is 

 much more detrimental than the gradual loss of the same 

 quantity. If a large artery, such as the carotid or femoral, 

 is opened, the sudden outpouring will rapidly exhaust the 

 vital forces by disturbing the equilibrium of the cardiac 

 movements. When the flow is gradual the heart will only 

 yield to the depressing effect when the aortic pressure is 

 markedly diminished, which event occurs after about 2}^ 

 per cent of the entire weight of the body is lost in blood. 

 Thus a horse weighing 1,000 pounds may lose 25 pounds 

 of blood before there is any manifest influence upon the 

 heart. Two per cent of the body weight may be drained 

 out with impunity, three per cent will cause a transient de- 

 pression of the vital forces, four per cent will endanger 

 the heart's action and larger quantities will threaten life 

 according to the amount withdrawn and the regenerative 

 vitality of the subject. Healthy horses may lose from i to 

 i^ per cent of their entire weights in blood, weekly, and 

 maintain a good condition of health, as has frequently been 

 shown on animals used for the production of antitoxins. 



The bleeding animal is protected against death by the 

 contractility of the arteries, which accommodate them- 

 selves 10 the diminishing volume until the quantity lost 

 reaches a certain amount. And besides, when the flow is 

 gradual, the capillaries replenish the supply by absorbing 

 liquids in the tissues, which fact accounts for the greater 



