vi ALBUMIX-DYE COMPOUNDS 225 



Lehmann, 1 and others, casein is calcium caseinogenate. The reserve- 

 material in the seeds of plants, the crystalline phyto-vitellines, seem 

 to occur always in the form of their calcium and magnesium salts, 2 

 and as such they also crystallise most readily under artificial con- 

 ditions. Osborne 3 rightly points out that observers have frequently 

 examined these albumin-salts under the belief that they were dealing 

 with pure albumins. 



Albumins form insoluble salts with the heavy metals, and hence 

 ferric chloride, copper sulphate, etc., are used for precipitating 

 albumins. (See p. 303.) 



Organic bases will also combine with albumins to form salts : 

 Spiro 4 showed that the denaturalised albumin 'albuminic acid,' 

 combined with cholin, pyridin, anilin ; further, with such basic sub- 

 stances as urethane, urea, thiourea ; finally, also with oil of mustard. 

 The importance of these bases, of the calcium salts, etc., is discussed 

 under the heading of Coagulation in Chapter VIII. 



IV. THE SALTS FORMED BY THE UNION OF ALBUMINS WITH 

 ANILINE DYES 5 



That histological staining reactions are microchemical reactions 

 has been held for a long time by Miescher, 6 Ehrlich, 7 Knecht, 8 

 Knecht and Appleyard, 9 Malfatti, 10 Mann, 11 E. Zacharias, 12 Lilienfeld, 13 



1 W. Hempel and J. Lehmann, Pftuger's Arch. f. d. ges. Physiol 56. 558 

 (1894). 



2 0. Schmiedeberg, Zeitschr. f. physiol. Ghem. I. 205 (1877) ; G. Griibler, Journ. f. 

 prakt. Ghem. 131 (2 F. 32), 97 (1881). 



3 T. W. Osborne, Journ. of the Amer. Ghem. Soc. 21. 486 (1899). 



4 K. Spiro, Zeitschr. f. physiol. CJiem. 3O. 182 (1900). 



5 A full account will be found in Mann's Physiological Histology, 1902, pp. 327-370. 



6 Miescher, Verh. d. naturf. Ges. in Basel, 6. 138-208 (1874). 



7 Ehrlich, Farbenanalytische Untersuchungen z. Hist. u. Klinik. d. Blutes, Berlin, 

 1891, Hirschwald. 



8 Knecht, Ber. d. deutsch. chern. Ges. 21. 1556 (1888) ; Rev. Gfrn. des Mat. Col. 

 4. 251 (1900) ; Ber. d. deutsch. chem. Ges. 35. 1022 (1902). 



9 Knecht and Appleyard, ibid. 22. 1120 (1889). See also Knecht, Rawson, and 

 Loewenthal, Handbuch der Farberei d. Spinnfasem, Berlin, 1895. 



10 Malfatti, Ber. d. naturw. med. Vereins in Innsbruck (1891-92). 



11 G. Mann, 'The Embryo -sac of Myosurus minimus: a Cell Study,' Trans, and 

 Proceed, of Bot. Soc. Edinburgh, 1892, p. 351; "The Functions, Staining Reactions, 

 and Structure of Nuclei,' Brit. Assoc. for the Advancement of Science, 1892, p. 753 ; 

 Physiological Histology, 1902, pp. 365-369. 



12 Zacharias, Ber. d. deutsch. bot. Ges. 11 (1893). 



13 Lilienfeld, Arch. f. Anat. u. Physiol. (1893) ; and in Zeitschr. f. physiol. Chem. 

 18. (1894). 



Q 



