PRECAUTIONS REGARDING BLOOD-LETTING 143 



changes. A full bleeding diminishes the activity of all 

 vital functions, excepting the production of blood corpuscles. 

 The heart-beat is quickened, but its force is lessened ; 

 arterial tension is lowered ; absorption is increased ; sensi- 

 bility to pain is diminished, owing to reduced activity of 

 the peripheral centres. When blood is lost rapidly or 

 freely, sighing, yawning, fainting, and convulsions ensue, 

 and artificial anaemia is produced. In healthy subjects, 

 however, these effects quickly disappear, and the blood is 

 rapidly restored to its normal state. 



Until within the last forty years, blood-letting was freely 

 practised, and very generally abused. Venesection is now 

 seldom employed even in cases of acute congestion and 

 inflammation, which it is especially fitted to control. It may 

 be practised either generally or locally. In robust animals 

 suffering from acute congestion of the lungs, especially 

 when accompanied by venous stasis, blood-letting affords 

 prompt and frequently permanent relief. Alike in horses 

 and cattle, it is serviceable where fever is acute, with a firm, 

 incompressible, or full, slow pulse, as in laminitis, as well as 

 in acute rheumatism. In some cases of lymphangitis in 

 horses it is also useful. Dogs are so readily brought under 

 the influence of emetics and nauseants that bleeding is less 

 needed in them than in horses and ruminants. 



Blood may generally be taken from full-grown horses or 

 cattle to the extent of three or four quarts. The amount 

 drawn should be accurately measured. The circumstances 

 of the case materially affect the amount of blood to be 

 drawn. It should flow freely until its abstraction has made 

 a decided impression on the volume and strength of the 

 pulse, or until the earliest symptoms of nausea and fainting 

 are apparent. The jugular vein on either side is generally 

 selected as the vessel on which it is most convenient and safe 

 to operate. Excepting in expert professional hands, the 

 fleam is safer than the lancet, which in restive horses may 

 make an ugly gash. When practicable, the horse should be 

 bled with his head erect, for in this position the nauseating 

 effects, which indicate that no more blood can be spared, are 

 most noticeable. When sufficient blood has been taken, the 

 edges of the wound of the skin are brought accurately 



