298 THE HUMAN BODY 



adult male is stated at 5,000,000 per cubic millimeter (-, R/Uo cubic 

 inch); for the adult female the figure is half a million less. The 

 method of determining this number is to draw from the ear or 

 finger tip an accurately measured volume of blood; this is diluted 

 to a known volume and the number of corpuscles in a known 

 amount of this diluted blood is counted under the microscope. 

 From this the total number in any volume of undiluted blood 

 can easily be calculated. 



It must be remembered that the liquid part of the blood is 

 subject to changes of volume, either in the way of increase as 

 liquid is received into it from the digestive tract, or decrease as 

 liquid passes from it into the lymph; therefore a variation in the 

 number of red corpuscles per cubic millimeter does not necessarily 

 mean a corresponding variation in the total number in the Body. 



Hemoglobin. This substance, which is a compound of a pig- 

 ment with a protein (see Chap. I), is the functionally important 

 part of the red corpuscle, the stroma serving merely as a frame- 

 work upon which it is carried. Its importance lies in the fact 

 that it combines readily with oxygen, forming a loose combina- 

 tion which can easily be broken up, thus it serves to transport 

 oxygen from the lungs to the tissues of the Body (see Respira- 

 tion). This property seems to be associated with the presence 

 of iron in the pigment part of the hemoglobin molecule. 



In the adult male about fourteen parts in the hundred by 

 weight of the blood are hemoglobin. It has been estimated that 

 a man weighing 68 kilograms (150 Ibs.) has in his blood 750 grams 

 (1.64 Ibs.) of hemoglobin, which is distributed among some 

 25,000,000,000,000 red corpuscles, giving a total superficial area 

 of about 3,200 sq. meters (3,800 sq. yds.) of hemoglobin. On ac- 

 count of the very rapid circulation of the blood (see Circulation) 

 practically the whole of this great area of hemoglobin is poured 

 through the capillaries of the lungs every thirty seconds, so it is 

 apparent that we have here a remarkably efficient arrangement 

 for supplying the Body with oxygen. 



There is a pathological condition known as anemia in which 

 there is a considerable reduction in the number of red corpuscles. 

 This is usually accompanied by a diminution in the amount of 

 hemoglobin contained in each corpuscle, so that as a result there 

 is a serious shortage in the hemoglobin content of the Body. Per- 



