THE BLOOD 25 



The same observer gives the amount of blood in the body of 

 the horse at 29 litres (66 pounds, or nearly 50 pints). 



The Distribution of Blood in the Body (Fig. 9) is believed to be 

 as follows : 



About one-fourth in the heart, lungs, large vessels, and veins, 

 liver. 

 „ „ skeletal muscles. 



„ „ other organs. 



It is probable that in the horse the liver would contain less 

 than one-fourth the bulk of blood, while the skeletal muscles 

 would contain more. Under certain conditions the abdominal 

 veins are capable of containing the whole of the blood in the 

 body. When an organ is active it receives more blood than when 

 in a state of rest ; this increase has been variously estimated at 

 from 30 to 50 per cent. 



Fig. 9. — Diagram to illustrate the Distribution of the Blood in the 

 Various Organs of a Rabbit, after Ranke's Measurements (Stewart). 



The numbers are percentages of the total blood. 



Regeneration of the Blood after Haemorrhage. — Regeneration 

 of the fluid portions of the blood is extremely rapid, experiments 

 showing that after slight haemorrhage the normal volume is 

 regained within a few hours, and after severe haemorrhage in 

 from twenty-four to forty-eight hours. This is supported by 

 clinical observation ; in the days of severe bleedings venesection 

 to the extent of producing syncope was frequent, yet in a very 

 short time the volume was restored. In these cases it is the 

 plasma which is rapidly replaced. The red cells and haemoglobin 

 take longer to prepare, probably several days, perhaps even two 

 or three weeks. In the dog exact observation shows that a 

 haemorrhage of from 2 to 3 per cent, of the body weight is readily 

 recovered from, while a loss of 4*5 per cent., which represents half 

 the blood in the body, is generally fatal. Percivall tells us* that 

 in the horse he occasionally drew 3 gallons of blood, which may 

 be taken as half the amount in the body, apparently without 

 fatal consequences. 



* ' Hippopathology,' vol. i., p. 95. 



