BEER WORT 



175 



2. Peel and take out the eyes. 



3. Remove cylinders from the longest diameter of 

 each potato by means of an apple-corer or a large cork- 

 borer (i. e., one of about 1.4 cm. diameter). 



The reaction of the fresh potato is strongly acid to 

 phenolphthalein. If, therefore, the potatoes are re- 

 quired to approximate +10, as for the cultivation of 

 some of the vibrios, the cylinders should 

 be soaked in a i per cent, solution of 

 sodium carbonate for thirty minutes. 



4. Cut each cylinder obliquely from end 

 to end, forming two wedge-shaped por- 

 tions. 



5. Place a small piece of sterilised cot- 

 ton-wool, moistened with sterile water, at 

 the bottom of a sterile test-tube; insert 

 the potato wedge into the tube so that 

 its base rests upon the cotton- wool. Now 

 plug the tube with cotton- wool (Fig. in). 



6. Sterilise in the steamer at 100 C. for 

 twenty minutes on each of five consecutive 

 days. 



NOTE. The cork borer reserved for cutting the 

 potato cylinders should be silver electro-plated both 

 inside and out, and the knife used for dividing the 

 cylinders should be of silver or silver plated. When 

 these precautions are adopted the potato wedges 

 will retain their white color and will not show the discoloration 

 so often observed when steel instruments are employed. 



Beer Wort. Wort is chiefly used as a medium for 

 the cultivation of yeasts, moulds, etc., both in its 

 fluid form and also when made solid by the addition of 

 gelatine or agar. The wort is prepared as follows : 



1. Weigh out 250 grammes crushed malt and place 

 in a 2-litre flask. 



2. Add 1000 c.c. distilled water, heated to 70 C., 

 and close the flask with a rubber stopper. 



FIG. in. 

 Potato tube. 



