210 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



These yield, on treatment with dilute acids or alkalis, 

 solutions containing acid or alkali-albumins (p. 185). 



By heating with acids or by the action of enzymes such 

 as pepsin or trypsin, albumins are gradually broken down, 

 yielding successively : 



1. Albumoses precipitated by alcohol and by ammonium 

 sulphate. 



2. Peptones precipitated by alcohol but not by ammonium 

 sulphate. 



3. Polypeptides, compounds which still give the biuret 

 reaction, are capable of synthesis by the condensation of 

 amino-acids, and can be further broken down to (pp. 201-202) 



4. Amino-acids and related substances, known as primary 

 disintegration products (pp. 192-201). 



BACTERIA AND PROTEOLYSIS 



If an ordinary plate culture is made from a small quantity 

 of sewage the gelatine will be found to liquefy round several 

 of the colonies. This liquefying action is not infrequently 

 so rapid and intense that a few liquefying organisms will 

 cause the whole plate to become liquid, before the remaining 

 colonies have time to develop. 



Such organisms manifestly play an important part in the 

 disintegration of albuminous matter. 



The action of these and other bacteria on the organic 

 matter of sewage has been the subject of a research by Messrs. 

 Clark and Gage of the Massachusetts State Board of Health. 

 They compared some 300 cultures of sewage bacteria, as regards 

 their ability to produce ammonia in peptone solution, to 

 reduce nitrates in nitrated peptone solution, and to liquefy 

 organic matter in the form of gelatine, during an incubation 

 period of seven days. 



The peptone solution consisted of O'l per cent. Witte's 

 peptone in distilled water, which gave an organic nitrogen 



