CHAPTER X 



THE PROTEIDS 



PROTEIDS are composed of one or of several albumins in combination 

 with a radical which is not an albumin, and which Kossel has called 

 the ' prosthetic group.' 1 As the peculiar properties of the proteids 

 are due to the prosthetic group, the latter is used for the classification 

 of the proteids. 



I. NUCLEO-PROTEIDS 



The nucleo-proteids were discovered simultaneously by Miescher 2 

 and P16sz 3 as constituents of the cell-nucleus. They are built up of 

 albumin and nucleic acid and always contain iron. 4 



(a) Nucleic Acid 



The nucleic acids contain phosphorus and nitrogen, but no 

 sulphur. They are organic acids of unknown constitution, although 

 their dissociation-products are fairly well known. In the year 1874 

 Miescher 5 discovered in the spermatozoa of the salmon an acid sub- 

 stance containing phosphorus, which he called nuclein. Altmann 6 in 

 1889 prepared from all nucleo-proteids the 'nucleic' acid, and proved 

 its identity with the nuclein of Miescher. The composition of nucleic 

 acid has been cleared up to a certain extent by Kossel 7 and his school. 



1 A. Kossel, Arch.f. (Anat. u.) Phys. 1891, p. 181 ; 1893, p. 157. 



2 F. Miescher, ' Chemische Zusammensetzung der Eiterzelle,' Hoppe-Seylers Med.- 

 chem. Untersuch. p. 441 (1871). 



3 P. Plosz, 'Kerne der Vogel- und Schlangenblutkorperchen,' ibid. p. 461 (1871). 



4 See index under iron. 



5 F. Miescher, Verh. d. naturforsch. Ges. in Basel, 6. Heft 1, 138 (1874). 



6 R. Altmann, Arch.f. (Anat. u.) Physiol. 1889, p. 524. 



7 A. Kossel, Zeitschr. f. physiol. Chem. 7. 7 (1882) ; Arch. f. (Anat. u.) Physiol. 

 1893, p. 157, and Liebreich's EnzyJdopadie, III. Bd. ' Nucleiustoffe ' (in both works are 

 reviews) ; A. Kossel and A. Neumann, Ber. d. deutsch. diem. Ges. 27. II. 2215 (1894). 

 The other papers are indicated in the following pages at their proper places. 



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