IOO 



SOLID .CULTIVATION MEDIA. 



and the plug is replaced immediately afterwards. This process is 

 repeated till a sufficient number of tubes are prepared ; and the test- 

 tubes thus charged with serum are at once placed in the " slow 

 steriliser" (see Fig. 52), the temperature of which is raised to 

 57 C. At this temperature, which must on no account be more 

 than very slightly exceeded, the apparatus is maintained for six hours 

 on the first day of the sterilising process. On each of the five 

 succeeding days the apparatus must again be raised to the same 

 temperature, and maintained there for four hours each day. The 



Fig. 53. —Slow steriliser for blood serum. 



a. Main chamber with water jacket. 



b. Central tube communicating with water in jacket. 



c. Lid with diverticulum, heated by Bunsen burner, d. 

 Thermometers pass into central chamber, lid, and water-jacket. 



temperature is not allowed to mount higher, lest premature coagula- 

 tion should occur in the serum, and its transparency should thus be 



