THE CHEMISTRY OF ALBUMINS 211 



value (determined by the Kjeldahl method) of 14 parts nitro- 

 gen per 100,000. The nitrat«d peptone solution contained, in 

 addition, nitrate equivalent to 10 parts nitrogen per 100,000. 

 The Uquefying power was determined by taking test-tubes of 

 uniform bore filled to a depth of 100 mm. with standard beef 

 peptone gelatine. The entire surface was inoculated, and 

 the depth of liquefaction was measured after a given time. 



The general result of these researches was to show that, as 

 a rule, the liquefjnng power was sjmonymous with increased 

 ability to reduce nitrates and to ammoniafy peptone. 



In order to determine whether a liquefying organism 

 secretes a proteolytic enzyme, about 0'5 per cent, of thymol 

 may be added to the liquefied gelatine, to inhibit further 

 bacterial activity, and a measured quantity of the liquid 

 thus obtained, say 0"1 c.c, placed on the surface of nutrient 

 gelatine, containing also 0'5 per cent, of thymol, in a tube of 

 uniform bore. The liquefaction of the gelatine can be readily 

 observed, and by taking different strengths of the liquid con- 

 taining the enzyme, quantitative measurements can be made. 



Reference may here be made to the activity of proteolytic 

 organisms in the so-called ' bating ' or ' puering ' process in 

 the tannery. In this process the skins, which have been ' de- 

 haired ' by lime, are immersed in a bath or ' bate ' of pigeon's 

 or dog's dung. The bacteria present produce digestive enzymes, 

 which have a solvent action on the fibres of the skin, rendering 

 it more supple. At the same time the acids, ammonia and 

 amines which are produced assist in the solution of the 

 lime remaining in the skin from the de-hairing operation. 



In order to avoid the use of the unpleasant ' bate ' or ' puer ' 



above mentioned, and with the object also of more accurately 



controlling the process, J. T. Wood, in conjunction with Popp 



and Becker, has successfully made use of a puer-substitute, 



termed ' erodin,' which consists of a culture medium of 



peptonised gelatinous tissue, with a special mixed culture of 



selected bacteria. 



p2 



