THE BLOOD 203 



often found enclosed in large phagocytes. The iron is often 

 very abundant after a marked destruction of erythrocytes. 



YI. 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 





FlG. 103. Section of Red Marrow of Bone. a. , lymphocyte ; b. , fat cell ; 

 c. , erythroblast ; d., giant cell; e. , erythrocyte ; /.,' erythroblast in 

 mitosis; g. , neutrophil myelocyte ; A., eosinophil myelocyte ; k., 

 eosinophil leucocyte ; I. , polymorpho-nuclear leucocyte. 



used, determining the amount of haemoglobin in it to ascer- 

 tain the amount of blood it represents. By this method 

 the amount of blood was found to be about T V of the body 

 weight. 



Haldane and Lorrain Smith have devised a method which 

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

 fact that after a person has inhaled carbon monoxide it is 

 possible to determine to what proportion the gas has replaced 

 oxygen in the oxy haemoglobin. If then an individual breathes 

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

 men of blood contains a definite percentage of the gas, the 



