NUTRIENT MEDIA AXD METHODS OF CULTIVATION. 



101 



isqueeziug through a linen cloth ov a meat press. The reil juice tlius 

 obtained must be bi'oug'ht up to a litre b}' transferi'ing it to a large 

 measuring glass and ailiUng distilled water. It is then poured 

 into a sutiiciently large and strong beaker, and set aside after tlie 

 addition of 10 grammes of peptone, 5 grammes of common salt and 

 lOO grammes of best gelatine. 



In about half an hour the gelatine is sufficient]}' softened, and 

 subsequent heating in a water-bath causes it to l)e completel}' 



Fig. .30. — Hot Aih Stehiliseh. 



dissohed. The danger of lareaking the l)eaker may be avoided by 

 placing a cloth, sevei-al times folded, at the bottom of the water-)>ath. 



The next process requires the greatest care and attention. 8ome 

 micro-organisms grow best in a slightly acid, others in a. neutral 

 or slightly alkaline, medium. For example, for the growth and 

 characteristic appearances of the comma Ijacilhis of Asiatic cliolera 

 a faintly alkaline soil is absolutely essential. This slightly alkaline 

 medium will be found to answer best for most micro-organisms, and 

 may be oljtained as follows : — 



With a clean glass I'od dipped in the mixture, the reaction 

 upon litmus-papei' may be ascertained, and a concentrated solution 

 of carbonate of soda must be added drop by drop, until red litmus- 



