90 HIGH TEMPERATURE ORCAXISM OF FERMENTING TAN-BABK, 



compared with earlier examinations. So pronounced was this that the flask was 

 reseeded on the thirteentli (hiy. with the same race, 80. 



When the bacteria appeared in the control, 0.5 gi-am ot crystal violet was addetl 

 and this caused a sharp fall in the evolution of gas. The activity of the bacteria 

 had been checked and the carbon dioxide that appeared on the fourteenth day 

 may be looked upon as partly residual and partly chemical. The disinfectant 

 did not destroy all the bacteria, but it seemed to hold them in check. On the 

 nineteenth day living bacteria were still in the control flask and on the twentieth 

 day 0.5 gram of mercuric chloride was added. 



The rise on the fourteenth day was followed by a fall on the fifteenth and 

 as the yield remained steady for another day, it was considered that a further 

 addition of sodium hydrate might be made. Five c.c. of normal soda were added 

 to each flask and although this caused a slightly increased evolution of gas yet 

 the increase was so little that a further 10 c.c. of soda were added. The yields 

 remained almost constant for several days, and the conclusion was made that the 

 amount of alkali added up to the eleventh day, viz., the equivalent of 16.4 c.c. 

 of normal sodium hydrate was sufficient for the 30 grams of bark. On the 

 twentieth day it was considered that the experiment had reached an end and, as 

 a final cast, it was decided to try the influence ot the addition of a nitrogenous 

 nutrient. The previous experimental evidence was in favour of asparagin, and 

 accordingly 0.25 gram was added to each flask. 



The effect of the asparagin was very marked and clearly indicated the 

 necessity of the addition of a niti-ogenous nutrient for a very active fermentation 

 of tan-bark. There is, of course, the possibility that the carbon of the asparagin 

 was quickly oxidised to carbon dioxide and the increase was derived from the 

 asparagin directly. It this were the ease, the 0.25 gram of asparagin is capable 

 of giv-ing 333 milligrams of CO2. Before the addition of the aspara- 

 gin, the evolution of CO2 had been fairly constant at 55 milligrams. 

 During the eight days following the addition, the excess over the 55 milligram 

 mark totalled 623 milligrams, which is more than could be credited to the a.spara- 

 gin. It follows that there is an insufficiency of nitrogen in the bark tor its 

 complete fermentation. 



An experiment with tempered hark, and parallel to Ihe last with tan-bark, 

 was started one day later. During sterilisation, the temperature, starting at 

 164°, rose in an hour to 200°, then fell gradually to 176° by the end of the 

 second hour. Thirty gi-ams of the bark dried at 130° were taken for each por- 

 tion. Fifty c.c. of water containing a suspension of race 80 were added to the 

 test flask and the same ijuantity of water to the conti'ol. 



