APPENDICES 647 



II. CLASSIFICATION OF THE PROTEINS. 



I. Native Proteins. 



A. Uncombined. 



1. Poor in Di-amino Acid's. 



(i.) Albumins.— Coagulated on heating; soluble in water ; 



not precipitated by half saturation with (NH4)oS04. 



(ii.) Globulins.— Coagulated on heating; insoluble in 



water ; precipitated by half saturation with 



(NHJ.,S0,. 



2. Rich in Di-amino Acids. 



(i.) Protamines from the heads of spermatozoa, 

 (ii.) Histones from blood corpuscles, e.g. globin of haemo- 

 globin. 



B. Combined. 



1. Pbospho-proteins.— Yield phosphoric acid on decom- 



position, but not purin bases, e.g. vitellin of yolk of egg 

 and caseinogen of milk. 



2. Nucleo-proteins.— Compounds of protein with nucleic acid. 



The nucleo-proteins with the largest amount of nucleic 

 acid are called nucleins. Nucleic acid may be broken 

 down into phosphoric acid, a carbohydrate, purin bases 

 and pyrimidin bases. 



3. Gluco-proteins, e.g. mucin (p. 35). 



4. Cbromo-proteins, e.g. htemoglobin (p. 486). 



II. Modified Proteins. The Sclero-proteins. 



1. Collagen with its hydrate gelatin (p. 39). 



2. Elastin (p. 39). 



3. Keratin fp. 32). 



III. Products of Digestion of the Proteins. 



1. Proteoses (p. 16 et seq.). 



2. Peptones (p. 16 et seq.). 



3. Polypeptides (p. 19). 



