BY R. GREIG-PMITH. 



85 



Films prepared ut the eud of two days showed deeply staining rods in 

 each flask, and tubes seeded with the li(|Uors on the fourth day, gave bacterial 

 growths both in test and control. It is clear that an exposure to 150° for two 

 hours was not sufficient to sterilise the bark and thus the production of the 

 same amount of carbon dioxide in four days is explained. It was tht>ught that 

 the speed of the cuiTent of air passing through the flasks would have an influence 

 upon the results, but later observations showed that the quantity jjassing through 

 was sufficient to sweep out all the CO2 produced. The quantity passing through 

 per hour varied from 1.3 to 2.1 litres, with an average of 1.75. 



Pending the arrival of a quantity of stack and tempered barks, use was 

 made of tan-bark in an experiment similar to the jireceding. The preliminary 

 experiments did not promise that a satisfactory result would be obtained from 

 the untempered tan-bark, and it may be that the tannin remaining in the bark 

 restricts the activity of the bacteria. The bark was dried at 130° and two 

 portions of 24 gi-ams were weighed into flasks and sterilised at 150° to 190° for 

 three hours. This treatment was very drastic, but the previous experiment had 

 shown that two hours at 150° was not enough to destroy all the spores. The 

 control bark was wetted with 40 c.e. of N/'20 sodium hydrate and the test with 

 the same number of c.c. containing a suspension of the rods and spores of race 

 552 which actively decomposed saccharose in alkaline agar. 



Evolution of Carbon Dioxide from Tan-bark. 



442 

 528 

 598 

 654 

 095 

 7(i9 

 853 



Films were prepared at the end of the first day, and these showed faintly 

 staining rods and spores in the test fluid and nothing in the control. At the 

 end of the second day the control fluid was sterile and the test contained living 

 bacteria. As the liquid was found to be acid to litmus, 10 c.c. of sodium 

 hydrate were added to each flask. Upon the succeeding days, the acid reaction 



