THE PITUITARY BODY 



or protein-like substances. Generally, protein precipitants, 

 such as tungstic acid, phosphotungstic acid, or phospho- 

 molybdic acid (but not sulphosalicylic acid) free urine or a 

 solution of prolan more or less completely from the hormone, 

 particularly if protein is present or has been added. For 

 methods primarily based upon this behavior of prolan, see 

 the descriptions of Katzman and Doisy (1933, 1934), 

 Marshall (1933), and Zondek, Scheibler, and Krabbe (1933). 

 Katzman and Doisy were able almost completely to remove 

 prolan from very dilute solutions. 



Other methods of both initial preparation and subsequent 

 purification are more clearly dependent on the adsorption 

 of prolan to other substances. Among the adsorbents used 

 may be mentioned aluminum hydroxide (Reiss and Hauro- 

 witz, 1929), Lloyd's reagent (Davy, 1934), activated carbon 

 of vegetable or animal origin (Schmidt and Derankowa, 

 1931; Katzman and Doisy, 1932; Elden, 1933), kaolin 

 (Fischer and Ertel, 1931), permutit (Lejwa, 1932), and 

 benzoic acid (Katzman and Doisy, 1932, 1933). Funk and 

 Zefirow (1932) used either benzoic acid or quinine. Marshall 

 (1933) beheved that benzoic acid was an efficient adsorbent 

 only in the presence of protein. Apparently the most potent 

 preparations of prolan yet made, 3,000-30,000 "mouse-units" 

 per mg. (one "mouse-unit" = 0.3-0.03 7), were at least partly 

 purified by adsorption on benzoic acid (Katzman and Doisy, 

 1932; Haurowitz, Reiss, and Balint, 1933 [but also see 

 Haurowitz and others, 1934]). 



Marshall (1932) used filters of various porosities to free 

 prolan from part of the associated impurities. 



The chemical properties of prolan. — Properties which prolan 

 does not possess can be given with some assurance. Until it 

 has been isolated as a pure substance, however, less that will 

 ultimately be recognized as accurate can be said about its 

 chemical nature. Prolan in aqueous solution is rather rapidly 

 inactivated by heating (above 60° C.) especially if the solu- 

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