CHAPTER III 



VESSELS AND INSTRUMENTS USED IN CULTIVATIONS 



All instruments, jiesseh (flasks, test-tubes, beakers, cotton- 

 wool, filters, calico) to be used are first thoroughly sterilised 

 by heating. In the case of flasks and test-tubes, this can be 

 done by exposing them thoroughly in all parts to the open 

 flame of a large Fletcher's burner ; while thoroughly heated 

 the mouth is plugged with a good long plug (i to 2 inches) 

 of sterile cotton-wool, this being pushed in by means of 

 sterile forceps. The plug in all cases must not be loose, 

 but also not too firm — an error in the latter direction being 

 of course preferable to one in the former. Or the flasks and 

 test-tubes, instruments, cotton-wool, &c., are placed in an 

 air-chamber (see Fig. 4) heated by a large Fletcher's burner 

 for several hours, up to between 130° and 150" C. In the 

 case of small flasks, test-tubes, and cotton-wool this process 

 is of course much more convenient, since a large number 

 can be heated simultaneously. Beakers and glass filters to 

 be used merely for a temporary operation are placed over a 

 wire net on a tripod and heated by the flame of a Bunsen's 

 burner. In the case of test-tubes which are to receive 

 cultivation-fluids, I generally expose them, after having been 

 cleaned with strong acid, washed out with water and dried 



