BLEEDING. 95 



Quantity. — in order to reap the full advantages of 

 general bleeding, we must continue to draw blood until some 

 visible impression is made on the system. Some horses 

 will bear to lose a much larger quantity than others, with- 

 out our being able to explain the reason of the difference. 

 The quantity which an animal can lose will depend on his 

 condition at the time ; his age ; and on the nature of his 

 disease. Horses that work hard and live well, will bear 

 bleeding best ; fat subjects worse ; but poor animals worst of 

 all. Under acute inflammatory disease, an animal will 

 support the loss of a larger quantity than it could in 

 health. 



Under ordinary circumstances, a gallon is reckoned a 

 moderate bleeding : under pressing disease I occasionally 

 draw three gallons : I have heard oi four being taken ! A 

 gallon of blood may be reckoned equal to the loss of about 

 a pint in a man. Though under forms of disease we are in 

 the habit of prescribing so many quarts of blood to be drawn, 

 yet, when it becomes necessary to make a sensible impres- 

 sion on the system, our only safe guide is a steady obser- 

 vance of the eflPects produced on the pulse as the blood flows 

 through the arteries. 



The Effects of Abstraction will depend on two cir- 

 cumstances : on the quantity taken, and on the time it occu- 

 pies in flowing. The fuller and more rapid the stream, the 

 greater will be the efi'ect created by a smaller quantity : 

 when we are desirous, therefore, of producing " an impres- 

 sion on the system,^^ and to do this at the least possible ex- 

 penditure, we make a large opening. In order to know when 

 this impression is made, we keep our fingers steadily on the 

 pulse ; the declining force of the beats,, with their subsequent 

 total failure, indicate to us that the required effect is accom- 

 plished : this we call the sinking of the pulse. About the 

 time that the pulse " sinks," the animal commonly evinces 

 signs of uneasiness : it becomes fidgety ; jerks its head up 

 and down ; and moves step by step backward, until it has 

 gained the corner of the stable, where, finding a rest for the 

 hind quarters, it becomes once more tolerably tranquil. 



