CLASSIFICATION OF ALBUMINS 347 



especially by Pick, 1 has received a very strong confirmation through the 

 researches of E. Fischer and Abderhalden. 2 This classification assumes 

 the existence of two distinct radicals in the albumin-molecule, namely, 

 the hemi- and the anti-group, and has already been dealt with in full, 

 pp. 148-154. It shows that casein and prot-albumose form the hemi-end 

 of a chain, the anti-end of which is represented by gelatine and hetero- 

 albumose. Globin and the Bence-Jones' albumin resemble casein, 

 while edestin and serum-globulin approach gelatine in their constitution. 



All other albumins cannot be classified according to this scheme, 

 and other classifications, as, e.g., according to the amount of glutaminic 

 acid, 3 or cystin, 4 or tyrosin, 5 are arbitrary, and with our present 

 knowledge would account for only a certain number of albumins. 



It is to be regretted, but at present we have to be conservative, 

 and must retain the old classification which is based on the solubilities 

 and on the distribution of the different albumins, a classification which 

 goes back to the days of Hoppe-Seyler 6 and Drechsel, 7 and which has 

 also been adopted by Hammarsten. 8 



According to this classification, the naturally occurring, or native, 

 genuine albuminous substances, or the albumins in the restricted sense, 

 form the central group. They are characterised by possessing a colloidal 

 character when in solution, and by becoming denaturalised under 

 certain conditions. From these albumins are derived certain com- 

 pounds possessing definite features, namely, the acid -albumins and 

 the alkali -albuminates ; the albumoses, peptones and peptids ; the 

 halogen-albumins, etc. A third group contains the proteids, which 

 are compounds of an albumin with another radical, the so-called 

 ' prosthetic group.' 9 The albuminous portion of the proteids, namely, 

 the histones and the protamins, may be brought into line with the 

 true albumins. A fourth group is represented by the ' albuminoids ' 

 or albumins which form the firm supporting structures in the animal 

 body. The expression 'albuminoid' is not based on a chemical but 

 on an anatomical foundation, and is therefore, from a chemical point 

 of view, inadmissible. 



1 E. P. Pick, Zeitschr.f.physiol. Chem. 28. 219 (1899). 



2 E. Fischer and E. Abderhalden, ibid. 39. 81 (1903). 



3 F. Kutscher, ibid. 38. Ill (1903). 



4 K. A. H. Morner, ibid. 34. 207 (1901). 



5 F. Reach, Virchow's Archiv, 158. 288 (1899). 



6 F. Hoppe-Seyler, Handbuchder physiologisch- und pathologi sell- chemischen Analyse, 

 6. Aufl. p. 243 (1893). 



7 E. Drechsel, article ' Eiweisskorper ' in Ladenburg's Handworterbuch der Chemie. 

 3. 534 (1885). 



8 0. Hammarsten, Text-book of Physiol. Chemistry, 4. Aufl. 1899, p. 17. 



9 A. Kossel, Arch.f. (Anat. u.) Physiol. 1S93, p. 157. 



