BLOOD AND LYMPH 219 



VI. Total Amount of Blood in the Body 



This was formerly determined by bleeding an animal, 

 measuring the amount of blood shed, and determining the 

 amount of haemoglobin contained in it ; then washing out the 

 blood vessels, and after measuring the amount of fluid used, 

 determining the amount of haemoglobin in it to ascertain the 

 amount of blood it represented. By this method the amount 

 of blood was found to be about -^ s of the body weight in man. 



Haldane and Lorrain Smith have devised a method which 

 can be applied to the living animal. It depends upon the fact 

 that, after an animal or person has inhaled carbon monoxide, it 

 is possible to determine to v/hat proportion the gas has replaced 

 oxygen in the oxyhsemoglobin. If then an individual breathes 

 a given volume of carbon monoxide, and if a measured speci- 

 men of blood is found to contain a definite percentage of the 

 gas, the rest of the gas must be equally distributed through the 

 blood, and thus the amount of blood may be deduced. 



By this method they conclude that the blood is about ^ of 

 the weight of the body in the human subject. 



VII. Distribution of the Blood 



Roughly speaking, the blood is distributed somewhat as 

 follows : 



Heart, lungs, large vessels 



Muscles ...... 



Liver | 



Other organs 



VIII. Fate of the Blood Constituents 



The water of the blood, constantly renewed from outside, is 

 constantly got rid of by the kidneys, skin, lungs, and bowels. 



About the fate of the proteins we know nothing. They 

 are probably used in the construction of the tissues, but 

 experimental evidence of this is wanting. 



The glucose and fat are undoubtedly used up in the tissues. 



The urea and waste products are excreted by the kidneys. 



The fate of the salts is not fully worked out. The chlorides 



