PREPARATION OF NUTRIENT MEDIA. 83 



and 68 C. Directly solidification takes place the 

 tubes must be removed, and they should then 

 present the character of being hard, solid, of a pale 

 straw colour, and transparent. A little liquid 

 collects at the lowest point, and the serum is some- 

 times milky in appearance at its thickest part. The 

 serum may not only be employed in test-tubes, but 

 also in small flasks, glass capsules, or other vessels, 

 all of which should have to be cleansed and sterilised 

 in the usual way. Hydrocele fluid and other serous 

 effusions may be prepared in the same manner, or 

 gelatine may be added to the serum in the propor- 

 tion of 5 per cent. 



Inoculation of the Tubes. A small portion 

 of the material to be inoculated is taken up with 

 a sterilised needle or ose, and drawn in lines over 

 the sloping surface of the serum; or a minute piece 

 of tissue, tubercle, etc., may be introduced into the 

 tube and deposited on the surface of the nutrient 

 medium. The precautions that are to be observed 

 in isolating the material to be inoculated will be 

 referred to later (p. 97). 



LIQUID MEDIA. 



(E) PREPARATION OF STERILISED BOUILLON, LIQUID 

 BLOOD SERUM, URINE, MILK, VEGETABLE INFU- 

 SIONS, AND ARTIFICIAL NOURISHING LIQUIDS. 



Nutrient liquids are still largely employed, and 

 by some observers even in preference to the solid 



