REACTION OF BLOOD 77 



One-fourth in the heart, lungs, large arteries, and veins. 



One-fourth in the liver. 



One-fourth in the skeletal muscles. 



One-fourth in the remainder of the body. 



Composition of Blood. The blood consists of a fluid 

 plasma (liquor sanguinis), in which are suspended cells called 

 blood corpuscles. It may be regarded as a tissue of which the 

 intercellular matrix is a fluid. Freshly drawn, it is of a bright 

 scarlet color when taken from the arteries or pulmonary veins, 

 but crimson when taken from the systemic veins. This is 

 the result of different oxidation stages of the pigment hemo- 

 globin, which is contained in the red corpuscles. The blood 

 is opaque, caused by the fact that its solid elements oppose 

 the transmission of light by reflecting it back from their sur- 

 faces. In various ways, as by the addition of ether, bile, excess 

 of water, by freezing and thawing, etc., the coloring matter 

 may be driven from the corpuscles into solution in the plasma, 

 leaving a delicate, colorless cell body, through which the light 

 passes readily. The blood is then transparent, and is known 

 as laky blood. The specific gravity varies from 1041 to 1067, 

 according to age, sex, state of health, meals, exercise, and 

 sleep. Its slightly alkaline reaction to litmus is due to the 

 phosphates and carbonates of the alkaline metals. Estimated 

 as sodium carbonate, it is equal to 0.35 per cent. Ordinary 

 litmus paper cannot be used in testing the reaction of the 

 blood, owing to the fact that it stains red with hemoglobin. 

 Soaking in saturated salt solution covers the paper with a layer 

 of salt that holds the corpuscles, which may then readily be 

 washed off. 



Reaction of Blood. The question of the reaction of the 

 blood has, with the development of physical chemistry, received 

 far greater definiteness. It, as well as most of the normal 

 body fluids, is, so far as the relative content in H and OH 

 ions is concerned, neutral. Ordinary indicators are affected 

 differently by the same solutions. Thus phenolphthalein 

 reacts neutral with blood instead of alkaline, as does litmus. 

 In determining the alkalinity of the blood by titrating with 

 weak tartaric acid, this acid is sufficiently strong to drive the 

 sodium out of its weak combination with carbonic or phos- 

 phoric acid ? This method indicates, therefore, the dissociable 



