CULTURE MEDIA 



forty-eight hours in order to eliminate those that have 

 been contaminated. Store the remainder in a cool 

 place for future use. 



Alternative Method. 



Steps 1-5 as above. 



6. Sterilise the serum by the fractional method 

 that is, by exposure in a water-bath to a temperature 

 of 56 C. for half an hour on each of six consecutive 

 days ; store in the fluid condition. 



7. Coagulate in the inspissator when needed. 



::::: ' 



FIG. no. Serum inspissator. 



Serum Water. 



This forms the basis of many useful media, and is prepared as 

 follows : 



1. Collect blood in the slaughterhouse (see page 168) and when 

 firmly clotted collect all the expressed serum and measure in a 

 graduated cylinder. 



2. For every 100 c.c. of serum add 300 c.c. distilled water and 

 mix in a flask. 



3. Heat the mixture in the steamer at 100 C. for thirty min- 

 utes. (This destroys any diastatic ferment present in the serum 

 and partially sterilises the fluid.) 



4. Filter if turbid. 



5. If not needed at once complete the sterilisation of the serum 

 water by two subsequent steamings at 100 C. for twenty minutes 

 at twenty-four hour intervals. 



