232 Infestation of Fimf/us Cultures by Mites 



appeared to be some escape of Pyridine when the cultures were incu- 

 bated at 25° C. The yields were weighed after a period of three weeks. 

 An inspection of Table VIII brings out with startling clearness the large 

 differences in yield that ensue through the minimising of the toxic effect 

 of Pyridine by the addition of amounts of acid in quantities sufficient 

 partially to neutralise the base. 



Table VIII. 



Toxicity of Pyridine to Aspergillus niger. 



Culture solution Coons' double strength. 



Pure Pyridine S.G. -983 added. 



Culture and organism. Aspergillus niger from Lister Inst. No. 594. 



Period of incubation 21 days. 



Temperature of incubation 18*^-19° C. 



Description of test 

 Control (no Pyridine) 

 Control „ 



Control „ 



Pyridine added and acid to adjust ^jH to 4-7 



No. 



CI. 



C2. 



C3. 



P.s. 1. 



2. 



3. 



4. 



5. 



6. 



7. 



8. 



9. 



10. 



11. 



12. 



13. 



P. 1. 



2. 



3. 



4. 



5. 



As we wished to trace the toxic action of Pyridine completely, and 

 as these results indicated that our initial additions of Pyridine were too 

 large, a fresh series of experiments was set up commencing with an 

 extremely small dose (about -005 per cent.) and ranging up by small 

 additions to concentrations that experience showed were sufficient to 

 inhibit growth completely. The greatest care was taken to ensure that 



Pyridine added. No 



adjustment of pH 



