BLOOD AND BLOOD DERIVATIVES — COHN 



423 



The methods of the nineteenth century have been largely supplanted 

 by recent developments in the preparative chemistry of the proteins 

 and upon two of these are based the preservation and accumulation as 

 against military needs in distant theaters of operation of the plasma 

 proteins separated from the blood collected by the American Bed Cross. 



The first of these methodical developments is the drying of proteins 

 from the frozen state. Proteins coagulate at elevated temperatures and 

 in the presence of the organic solvents generally used in drying ordi- 

 nary chemicals. Likewise, denaturing changes often take place when 

 proteins are dried at ordinary temperatures. A body of investigation 

 has demonstrated, however, that such changes are minimized when 

 protein systems are first reduced to the frozen state and water then 

 removed under reduced pressure by sublimation. The dried plasma 

 which has so successfully been used by our Armed Forces in every 

 theater of operation is rendered stable by this technique. The plasma 

 is reconstituted just before use by addition to the dried powder in one 

 bottle of the diluent transported in another bottle in the same package. 

 All but the most labile components of plasma may be preserved by 

 this process, whereas all but its colloidal attributes are lost if liquid 

 plasma is preserved for long periods of time even at low temperatures. 



Table 3. — Distribution of proteins of plasma 1 



1 Conn, Oncley, Strong, Hughes, and Armstrong. 



> Estimated by electrophoresis. The amount of clottable protein is always lower and probably more 

 reliable. See Edsall, Ferry, and Armstrong. 



The second development has made possible the quantitatively repro- 

 ducible fractionation of plasma by new chemical methods which on the 

 one hand are susceptible to the large industrial scale that has been 

 necessary to process the blood of over one and one-half million Red 

 Cross donors, on the other to yield as final products plasma proteins of 

 unimpaired function. 



The potential value of all the different proteins of human plasma 

 demanded that this process be inclusive in the sense that all components 

 be separated and concentrated. The present process separates the 

 plasma into five fractions. (See fig. 2.) Fraction I is rich in fibrino- 

 gen. Fraction II consists of y-globulins, which are the chief bearers of 

 immunity in the blood. (For convenience in manufacture, Fraction 

 II + III, which contains essentially all the y-globulins, is first sepa- 



