272 PRACTICAL DAIRY BACTERIOLOGY 



dish and contents. Boil until all the agar is dissolved. Weigh 

 again and restore to original weight by adding water. 



&. Determine acidity. Neutralize and adjust reaction to 

 1.5% HC1, as described in 4, c. 



c. After obtaining the proper acidity bring the mass to a 

 brisk boil, and while it is boiling add to it the white of an egg, 

 previously mixed with a little water. Boil hard for 20 minutes. 



d. Weigh, and add water to bring it back to its original 

 weight. Bring to a boil. 



e. While boiling, as in d, place in a large funnel a consider- 

 able quantity of absorbent cotton. Over the top of the funnel, 

 or in a second funnel over the first, place some cheese cloth 

 (Fig. 72). Pour the hot agar mass through the cheese cloth 

 into the absorbent cotton. It will run through the cotton and 

 may be caught below in a flasl^. It should be transparent, clear, 

 and of a light yellowish-brown color. 



/. From the flask fill a number of sterilized test tubes, putting 

 about 10 c.c. into each. (Fig. 73.) Replace the cotton plug. In 

 filling these tubes it is best to use a funnel, and care should be 

 taken not to allow the agar to touch the tube where the cotton 

 is afterwards to be inserted, as it will stick to the cotton. 



g. Place the tubes, together with what remains in the flask, 

 in a steam sterilizer, figure 71, and allow the steam to act on 

 them for 20 minutes. Then remove and set aside in the temper- 

 ature of an ordinary room. 



h. 24 hours later put the material again in a steam sterilizer, 

 and sterilize for y 2 hour. 



i. 24 hours later sterilize again in steam for y 2 hour. The 

 material is now finished and may be preserved for future use. 



/. Agar slants. After the last steaming, while the agar in 

 the tubes is still hot and liquid, lay 20 of them down on a table 

 with their mouths slightly raised so that the agar will form a 

 slanting surface in the tubes. (Fig. 74.) Allow them to harden 

 in this position. 



