78 THE BLOOD 



sodium of the blood rather than the relative number of H and 

 OH ions. These are present in blood to about the same extent 

 as in water. The blood as it exists in the body always con- 

 tains a certain amount of CO 2 , NaHCO 3 , Na 2 HPO 4 , and also 

 sodium in combination with protein, which from this point 

 of view is a weak acid. These constituents are in an unstable 

 equilibrium, so that a considerable amount of acid or alkali 

 may be added without approximately altering its neutral 

 reaction. An important distinction is, therefore, to be borne 

 in mind, that is, the potential or titration reaction as contrasted 

 with the physicochemical or true reaction. 



Blood has a salty taste, and a peculiar, characteristic odor. 

 The temperature is about 98.9 F., but probably is higher in 

 the internal parts of the body. 



Corpuscles. The corpuscles of the blood are of at least 

 three kinds red corpuscles (erythrocytes) , white corpuscles 

 (leukocytes), and blood plates (microcytes) . The red cells may 

 be put at 5,000,000 per c.mm. for males, and at 4,500,000 

 for females, as an average number. Their number varies with 

 the constitution, nutrition, manner of living, and age of the 

 individual. They are most numerous in the embryo and 

 young. In the adult their number is at a minimum after meals ; 

 it is increased during menstruation, and decreased during 

 pregnancy. Change of altitude has been found to exert a most 

 remarkable influence. A mountain life has been found to 

 raise the average number to 8,000,000, and to increase the 

 contained hemoglobin as well. A return to a lower level brings 

 back the blood to its normal state. A diminished pressure 

 of oxygen in the blood, whether produced by high altitudes 

 or by the actual loss of blood, stimulates to greater activity 

 the tissues that form new corpuscles. When viewed under the 

 microscope individually, each corpuscle is of a faint yellowish 

 color. Each consists of an extensible, protoplasmic material 

 known as stroma, which gives shape to the corpuscle and holds 

 the hemoglobin. The latter, forming 90 per cent, of the solid 

 matter of the corpuscle, is held in some weak chemical combina- 

 tion with the stroma, since its behavior within the corpuscle 

 differs from that when separate. 



'Hemoglobin is a member of the group of combined proteins. 

 It may be separated in various ways into a protein body, 



