CULTURE MEDIA. 57 



wards they may be steamed for 15 to 20 minutes in the 

 sterilizer on 3 successive days. 



(6) Lorrain Smith's serum. To each 100 cc. of 

 serum add 1 to 1.5 cc of a 10 % solution of caustic soda. 

 Place in test tubes and treat as for Loeffler's serum. 

 Or the tubes may be slanted, covered with tin foil and 

 placed in the steamer with the lid raised and exposed to 

 the steam for one hour. Afterwards they may be 

 steamed for 15 to 20 minutes on 3 successive days. 



(c) Kanthack and Stephen's serum agar mixture. 

 In making this culture material it is first necessary to 

 determine the amount of 10% caustic soda (or potash) 

 that will be needed to transform the albumins of the 

 serum into alkali albumins, so that no coagulation 

 occurs on boiling. 2 cc. is about the usual amount re- 

 quired per 100 cc. of serum. 



To 100 cc. of the serum (or serous exudate) add 2 cc. 

 of 10 % caustic soda and 1 .5 grammes of prepared agar- 

 agar fibre. Boil up together and add 4 cc. glycerine 

 and .5 gramme of grape sugar. Again boil and filter, 

 using the warming funnel. 



This culture material can be treated as agar. It 

 possesses all the advantages of both serum and agar, 

 except the clearness of the latter material. 



Peptone solution of Dunham. To 100 cc. of dis- 

 tilled water add 1 gramme Witte's or Fairchild's pep- 

 tone and .5 gramme of common salt. Boil together for 

 15 minutes, neutralize if necessary with sodium carbon- 

 ate and again bring to a boil. Filter into flasks or 



