io VETERINAKY PHYSIOLOGY 



2. Synthesis of the Products of Disintegration 



Emil Fischer and his co-workers have succeeded in building 

 up from the amino acids a series of bodies containing two, four, 

 and as many as ten of the amino acid molecules, linked to one 

 another in series, the OH of the hydroxyl of one being linked on 

 to the amidogen of the other with the giving off of H 2 0, thus : 



H OH H H H 



H\ I II t t I I II 

 V>N-C-C N-C C OH 



I I 



H H 



Amino-acetic acid. Amino-acetic acid. 

 Glycin. Glycin. 



Glycyl-glycin. 



This he calls glycyl-glycin, the amino acids which have lost 

 the OH of the acid being characterised by the terminal yl. 



Such compounds he calls Peptides, characterising them, 

 according to the number of molecules linked, as Di-, Tri-, 

 Tetra-, and Poly-peptides. 



Some of the higher of these give the biuret test for proteins 

 from the presence of the linked CO.NH 2 group ; and if an acid 

 with the benzene ring is in the chain, they also give the xantho- 

 proteic test. 



He has also succeeded in building the pyrrhol derivative, 

 pyrrholidine carbonic acid, or prolin as he calls it, into 

 polypeptides. 



(C) Classification of the Proteins l 

 (A) Simple Proteins 



1. Native Proteins. These proteins, either alone, or combined 

 with certain other substances, are constant ingredients of dead 

 protoplasm and of the fluid constituents of the body. They are 

 distinguished from all other proteins by being coagulated on 

 heating. 



There are two groups Globulins and Albumins the former 

 characterised by being insoluble in distilled water, by requiring 

 the presence of a small quantity of a neutral salt to form a 



1 The general tests for proteins and the methods of separating the different 

 proteins must be studied practically. (Chemical Physiology.) 



