82 



SOLID CULTIVATION MEDIA. 



danger of contamination from the atmosphere is with certainty 

 excluded. 



Nutrient jelly in test-tubes is specially adapted for the cultivation 

 of those organisms which can subsist on concentrated animal food 

 material, and which grow at ordinary temperatures. At blood-heat 

 the five per cent, jelly becomes liquid, and thus it is not adapted for 

 the cultivation of organisms, which require so high a temperature to 

 maintain their growth. Notwithstanding these limitations to its use, 



Fig. 37. — Cultivation of B. anthracis in nutrient jelly, showing a 

 liquefaction of the upper portion. 



b. Dull yellow mass, composed of accumulated bacilli. 



c. Bacilli growing along the tracks of the inoculating needle. 



it is found to suit the requirements of a great number of species, and 

 is the more useful from its giving a characteristic reaction in the 

 presence of several of them. Organisms vary very much in the 

 reaction which they occasion in the jelly ; some have the peculiarity 



