230 EARL W. FLOSDOKF 



method of separating the various components of blood plasma. Some 

 of the fractions were freeze-dried in final form for actual distribution. 

 Penicillin, streptomycin, and other antibiotics have been freeze-dried 

 for distribution. Freeze-drying has been applied to the distribution 

 of many other products because of lability and because at the same 

 time there is greater ease of control of sterility as well as an increased 

 rate of solubility. This latter consideration is particularly important 

 where an ampule of the product must be opened by a physician and 

 dissolved at a temperature not lower than that of the room and not 

 above that of the body and made ready for immediate injection. 

 Rapid solubility frequently determines the suitability of a product for 

 clinical use. Freeze-dried preparations of hormones, parenteral 

 vitamin B preparations, enzymes, and other products are finding 

 continually wide; distribution. 



Highly purified tuberculin protein satisfactory for skin testing in 

 control of tuberculosis has been dried successfully by lyophilization. 

 Seibert, who has contributed more than anyone else to the chemistry 

 of tuberculin, has studied the effects of freeze-drying and various 

 procedures of applying it. She has found no change in this protein 

 material detectable by some of the most sensitive means available 

 today (32). Langner and associates have applied freeze-drying to 

 organisms for extraction and to extracts obtained from them in con- 

 nection with studies in allergy {33-35). Casals has applied freezing 

 and drying to various antigens of a nonvirulent nature to be used in 

 complement fixation tests with central nervous system virus infec- 

 tions. These have been frozen and dried and distributed to various 

 laboratories for use in hospital diagnostic work {36) . 



Smallpox and BCG vaccines are dried in the U. S. S. R. with ex- 

 cellent results for shipment to remote localities {37). Hetherington 

 has used lyophilized serum, embryo juice, and plasma media for 

 tissue culture {38) . An adequate supply of material can be kept on 

 hand for continued use to avoid considerable routine labor and at 

 the same time provide a constant medium for use in a long series of 

 comparative experiments. The product has been found excellent in 

 connection with the growth of cardiac explants for white mice. 

 Souter and Kark have produced a stable thromboplastin suitable for 

 use in the Quick prothrombin test {39). Material ready for im- 

 mediate use vnth the addition of distilled water permits the perform- 

 ance of the test by the physician in his own office and makes it pos- 

 sible to carry out the test with greater ease anywhere. 



