BLOOD. 361 



weighing 68 kilos, has about 5236 grams, or 4965 c.c., of blood in his body ; 

 dog, 7.7 per cent.; rabbit and cat, 5 per cent; new-born human being, 5.26 

 per cent. ; and birds, 10 per cent. Moreover, the distribution of this blood 

 in the tissues of the body at any one time has been estimated by Ranke, 1 from 

 experiments on freshly-killed rabbits, as follows : 



Spleen 0.23 per cent. 



Brain and cord 1.24 



Kidneys 1.63 



Skin . . . ' 2.10 



Intestines 6.30 



Bones 8.24 



Heart, lungs, and great blood-vessels 22.76 



Resting muscles 29.20 



Liver 29.30 



It will be seen from inspection of this table that in the rabbit the blood of 

 the body is distributed at any one time about as follows : one-fourth to the 

 heart, lungs, and great blood-vessels; one-fourth to the liver; one-fourth to 

 the resting muscles ; and one-fourth to the remaining organs. 



Regeneration of the Blood after Hemorrhage. A large portion of the 

 entire quantity of blood in the body may be lost suddenly by hemorrhage 

 without producing a fatal result. The extent of hemorrhage which can be 

 recovered from safely has been investigated upon a number of animals. 

 Although the results show more or less individual variation, it can be said 

 that in dogs a hemorrhage of from 2 to 3 per cent, of the body- weight 2 is 

 recovered from easily, while a loas of 4.5 per cent., more than half the entire 

 blood, will probably prove fatal. In cats a hemorrhage of from 2 to 3 per 

 cent, of the body-weight is not usually followed by a fatal result. Just what 

 percentage of loss can be borne by the human being has not been deter- 

 mined, but it is probable that a healthy individual may recover without 

 serious difficulty from the loss of a quantity of blood amounting to as much 

 as 3 per cent, of the body-weight. It is known that if liquids which are iso- 

 tonic to the blood, such as a 0.9 per cent, solution of NaCl, are injected into 

 the veins immediately after a severe hemorrhage, recovery will be more certain ; 

 in fact, it is possible by this means to restore persons after a hemorrhage which 

 would otherwise have been fatal. The physiological reason for this fact seems 

 to be that the large access of neutral liquid puts into circulation all the red 

 corpuscles. Ordinarily the number of red corpuscles is greater than that neces- 

 sary for a barely sufficient supply of oxygen, and increasing the bulk of liquid 

 in the vessels after a severe hemorrhage makes more effective as oxygen-carriers 

 the remaining red corpuscles, inasmuch as it ensures a more rapid circulation. 

 If a hemorrhage has not been fatal, experiments on lower animals show that 

 the plasma of the blood is regenerated with astonishing rapidity, the blood 

 regaining its normal volume within a few hours in slight hemorrhages, and 



1 Taken from Vierordt's Anatomische, physiologische und physikalische Daten und Tabetten, Jena, 

 1893. 



2 Fredericq : Travaux du Laborataire ( Univei-site de Liege), vol. i., 1885, p. 189. 



