CIRCULATION 1 1 3 



They appear to be perfectly homogeneous, although there are indications 

 that some internal structural differentiation of parts exists. 



The striking visual characteristic of mammalian red cells is the absence 

 of a nucleus. This at once raises the question, "Are these cells really alive?" 

 Evidence has been presented that the life of any cell is in some way bound 

 up with the nucleus. Certainly, these red cells are alive during the early 

 stages of formation before they pass into the circulating blood. For at this 

 stage they possess perfectly normal nuclei. At this developmental stage 

 they must be considered alive. And, indeed, even the mature red cells of 

 vertebrates other than mammals are nucleated. But in man and other mam- 

 mals the nucleus is lost before the cell becomes a functioning unit. It may, 

 therefore be more accurate to refer to these structures not as cells but as 

 corpuscles — "httle bodies." Perhaps the relatively short period of time 

 during which red cells course through the blood stream — about ten to 

 thirty days, on the average — is in some way related to this absence of a 

 nucleus. 



HEMOGLOBIN 



The most interesting chemical entity in the cell is hemoglobin, which is 

 a protein (globin) in combination with an iron-containing pigment 

 (hematin). It constitutes 95% of the solids of these cells. Each 100 cc. of 

 blood contains a total of about 15 gm. of hemoglobin. The main func- 

 tions of the red corpuscles are carried out by means of this substance, 

 which incidentally, also confers upon blood its red color. This pigment 

 has the capacity for combining spontaneously with oxygen when free 

 oxygen is present in relative abundance in the environment. The union 

 is a loose one, so that, when the surroundings contain little or no free 

 oxygen, the oxygen breaks apart from the molecule and, by physical dif- 

 fusion, passes into the oxygen-poor regions. 



ANEMIA 



Anemia is an abnormality in which the red cells of the blood are re- 

 duced in number, or are deficient in hemoglobin, or both. Instead of a 

 normal count of about five million cells, the anemic individual may have 

 but four or three or even less than one million cells per cubic millimeter 

 of blood, depending upon the severity of the anemia. Anemia is an ab- 

 normal state in which there is a breakdown of the formation-destruction 

 balance which normally maintains the physiological constant of about 

 five million. 



The harm done to the organism in any anemia depends upon the chief 

 function of the red cells, namely, that of transportation of oxygen. If 

 there is a deficiency either of red cells or of hemoglobin, the quantity of 

 oxygen supplied to the tissues generally is reduced, cell oxidations are 

 hampered, energy liberation inadequate, and normal cellular function 



