416 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 5 



percent of hemoglobin contained in the red blood cell. Were this 

 concentration of hemoglobin free in the blood stream, it would bring 

 about a redistribution of many other components than oxygen. It is 

 the way of the body, or appears to be to those concerned with the 

 study of its mechanism, to evolve processes which in enhancing the 

 efficiency with which certain functions are performed do not inhibit 

 others. 



The function of transporting oxygen by the hemoglobin within the 

 red cell involves a complex mechanism permitting maximum combina- 

 tion with oxygen in the lungs and release of oxygen in the tissues. As 

 carbon dioxide increases, the hemoglobin unloads the oxygen which it 

 has transported. Another protein, an enzyme, carbonic anhydrase, 

 accelerates and renders more efficient this process. In addition, the red 

 cells contain other enzymes, including a catalase and a phosphatase. 

 The presence of these enzymes suggests the nature of certain of the 

 chemical reactions which are involved in the internal economy of these 

 cells. These vital processes also appear to limit the life of the red blood 

 cell. For the life of the red cell, estimated to be roughly 3 months in 

 the blood stream, is limited in the blood bank, under even the best 

 methods of preservation at present known, to approximately a month. 



No other part of human blood has so significant a function in trans- 

 porting oxygen to the tissues, in permitting the very great activity and 

 high order of mammalian respiration. Therapeutically, therefore, 

 when there is great blood loss from a wound, when a major operation is 

 to be performed, or when the anemia which frequently occurs in con- 

 valescence from wounds must be combated, red blood cells must be sup- 

 plied in amounts adequate to restore the oxygen-carrying capacity of 

 the blood. 



On the other hand, the lability of the red cells renders it difficult 

 to develop a reserve of whole blood which can be transported to the 

 theaters of operation at great distances and stored indefinitely against 

 the uneven needs of a military campaign. There are, moreover, many 

 functions of the blood other than those of oxygen transport. These 

 can be supplied by other parts of the blood, the more labile red blood 

 cells being conserved for therapy for conditions in which they alone 

 suffice. 



PLASMA AND THE PLASMA PROTEINS 



Blood is readily separated into cellular and noncellular parts by 

 centrifugation. The heavier cellular elements are easily thrown to the 

 bottom when the bleeding bottle is spun in a cup centrifuge. The 

 supernatant fluid is clear, amber colored, and is called the plasma. The 

 separated red cells occupy something less than half the total volume ; the 

 plasma, the body fluid in which they are suspended in nature, some- 



