434 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1945 



should be supplied in amounts adequate to restore the oxygen-carrying 

 capacity of the blood. 



Maintenance of blood volume by the proteins of the plasma, espe- 

 cially by the albumin, — Plasma, the fluid part of the blood, consists of 

 over 90 percent water and 7 percent protein. Of the proteins, ap- 

 proximately 58 percent is albumin, 14 percent a-globulin, 13 percent 

 /2-globulin, 11 percent y-globulin, and 4 percent fibrinogen. 



Plasma is used in military medicine in combatting shock and in the 

 treatment of burns. In burns there is often so large a loss from the 

 body of the diverse components of the plasma that their replacement 

 is necessary. In shock the function of the plasma is largely to restore 

 or maintain the blood volume so that circulation may remain normal. 

 The proteins dissolved in the plasma maintain the volume of the blood 

 by virtue of the osmotic pressure exerted largely by the albumin. 



Albumin, the most copious of the plasma proteins, exerts the largest 

 osmotic pressure and thus the largest effect in maintaining blood 

 volume. Its solutions are also the least viscous and for this reason 

 their injection should impose the smallest burden on the heart. Al- 

 though the smallest of the plasma proteins, albumin does not traverse 

 the blood-vessel walls in appreciable amounts under normal conditions. 



Storage and utilization of the proteins of the plasma in equilibrium 

 with the tissues. — The mechanism of control of the blood volume in- 

 volves the impermeability of the normal blood vessels to the plasma 

 proteins. If plasma proteins are injected in a normal person in excess 

 of need, certain of them leave the blood stream without appearing in 

 the urine and are presumably utilized as a source of energy or new 

 protein or are stored in the tissues. The injection of concentrated 

 serum albumin into the blood stream of a normal man is followed 

 by a rapid redistribution of protein between the blood stream and 

 the tissues. Further investigations are necessary to determine 

 whether this is regulated by colloid osmotic pressure, by subtle changes 

 in the permeability of the blood vessels, or specifically for each species 

 of plasma protein. Clearly there is interaction between the various 

 plasma proteins in the blood and the tissues in health and disease. 



Solution and transport of the lipids of the blood in more or less 

 labile combination with a- and ^-globulins. — Lipids of diverse kinds 

 are dissolved and transported in the blood, largely in combination, 

 more or less labile, with proteins. Fibrinogen, y-globulin, thrombin, 

 and albumin are poor, but a- and ^-globulin fractions are rich in lipid 

 material. The separation and further purification of these fractions 

 should increase our understanding of their chemical nature, phys- 

 iological function, and uses in therapy. 



Regulation of bodily function by hormones and enzymes of the 

 blood, — The hemoglobin of the red cells, the albumins and lipo- 



