i8 



a solid medium for cultivating bacteria at a high (body) 

 temperature. There are several processes for preparing 

 these media but the addition of the dry agar and gelatin to 

 bouillon (11) either immediately after it is filtered or 

 later after it has been sterilized and stored in flasks seems to 

 be the most convenient procedure. The agar itself is usually 

 neutral in reaction but the gelatin often has a decidedly acid 

 reaction. This necessitates the careful testing of the reac- 

 tion of the two media. 



14. General directions. Prepare 300 c.c. of agar and 

 300 c.c. of gelatin, i. e., start with 300 c.c. of bouillon for 

 each. There will be considerable shrinkage so that the 

 quantities of media will be appreciably less than this amount. 

 Distribute each medium as follows : 



Put 7 c.c. in each of 10 small sterile test tubes. 

 Put 12 c.c. in each of 12 large sterile test tubes. 

 Put the balance in a small sterile flask. 



$15. Nutrient gelatin. Take a flask of bouillon contain- 

 ing 300 c.c. and pour it into a small agate iron dish and add 

 30 grams of sheet gelatin, which has been cut into small 

 pieces, heat the bouillon, with frequent stirring, in a water 

 bath until the gelatin is dissolved. Allow it to cool to a 

 temperature between 45 and 50 C. and then add the white 

 of one egg and mix it thoroughly by stirring or better by 

 pouring the gelatin from one flask or beaker to another. 

 After the egg albumen is completely dissolved return the 

 liquid gelatin to the large covered water bath and boil until 

 the egg albumen is coagulated. This takes about 20 min- 

 utes. It is now ready for filtering which must be done while 

 the gelatin is hot. Filter through properly folded but 

 ordinary filter paper, first moistened with boiling water. 

 (For illustrations and directions for folding filter paper see 

 Abbott's Prin. of Bact. p. 82). Distribute the filtrate as 

 directed. In pouring the gelatin into the tube use a small 



