32 A MANUAL OF BACTERIOLOGY 



constant level. Both forms of Koch's ' steriliser are 

 covered externally with felt. 



The so-called steam digesters or ' autoclaves ' 

 are chiefly used in France. They are made of 

 stout copper, and are used for sterilising sealed 

 flasks (containing bouillon) under pressure. The 



temperature in 

 these digesters 

 often rises as high 

 as 120C. 



Besides the 

 above - mentioned 

 steam sterilisers, 

 there are those of 

 Herrmann and 

 Hirschberg, Ost- 

 walt, Muencke, 1 

 and Woodhead. 2 

 All these are use- 

 ful instruments, 

 and are to be re- 

 commended for 

 the bacteriological 



FIG. 10. HOT-AIR STERILISER. 



laboratory. 



Two forms of hot-air sterilisers are represented 

 in Figs. 10 and 11 respectively, and are used for the 

 sterilisation of flasks, test-tubes, cotton- wool, etc. 

 The former consists of a double wall of sheet-iron, 

 and the inner dimensions are 12 in. x 10 in. x 10 



1 Dingler's Polytechnisches Journal, 1885, Bd. 257, p. 283. 

 ' 2 Proceedings of Royal Physical Society of Edinburgh, vol. 

 ix. p. 524. 



