PREPARATION OF NUTRIENT MEDIA. 85 



for half an hour at 100 C. for two or three succes- 

 sive days. 



Liquid Blood Serum. The preparation of 

 sterile blood serum has already been described. It 

 may be used for cultivation, especially in the form 

 of drop- cultivations, before the final treatment by 

 which it is solidified. Hydrocele fluid, peritonitic 

 and pleuritic effusions, can also be employed after 

 sterilisation in the steam steriliser. The fluid should 

 be withdrawn with a sterilised trocar and canula, 

 and received into plugged sterilised flasks. 



Urine. In order to obtain urine free from micro- 

 organisms the following precautions must be ob- 

 served : The orifice of the urethra must be 

 thoroughly cleansed with sublimate solution. The 

 first jet of urine should be rejected, and the rest 

 received into sterilised vessels, which must be quickly 

 closed with sterile plugs. If these precautions be not 

 attended to the urine must be rendered sterile by 

 the means described for the sterilisation of bouillon. 



Milk. If milk has been drawn into sterile flasks 

 after thoroughly cleansing and disinfecting the 

 teats and hands, it may be kept without change. 

 If procured without these precautions it must be 

 steamed in the steriliser for half an hour for five 

 successive days. 



Vegetable Infusions. Infusions of hay, 

 cucumber, and turnip are used for special pur- 

 poses, and more rarely decoctions of plums, raisins, 

 malt, and horse-dung. They are mostly prepared 



