LABORATORY AND TEACHING METHODS 



609 



LESSON 15 



Potato Juice Agar (150 + 10 + 500). — Take 150 grams of peeled potato, slice 

 it thin, soak it in tepid water and allow it to simmer for half an hour. The juice 

 is used from this in place of bouillon in making the agar-agar. 



Potato Agar. — Put clean pared potatoes rapidly through a grater and immedi- 

 ately throw into the required quantity of distilled water, which should be used in 

 ratio of 2 c.c. of water to i gram of the potato. Then put in the Arnold sterilizer. 

 Soak the agar in water (i gram of agar to 100 c.c. of water), add to the potato and 

 mix thoroughly (Washington formula). 



Fig. 215. — Square form ut Arnold steam st 

 recommended by the Boston Board of Health. 

 cetitical Bacteriology, 191 2.) 



(Fi^ 



■, showing two front doors as 

 17, p. 42, Schneider, Pharma- 



Mel T. Cook's Formula. — Cook says 500 grams in 500 c.c. of water, 10 grams of 

 agar in 500 c.c. of water. 



Dr. Caroline Rumbold's Formula. — The freshly grated potato, 500 grams in 500 

 c.c. of water, is put in the Arnold steam sterilizer and heated up to 90°C. Part of 

 the pulp is strained through cheese cloth. 7.5 grams of agar are soaked in 500 c.c. 

 of distilled water and before the agar has dissolved, it is put into the potato, and 

 the whole thorughly mixed. It is then steamed by discontinuous sterilization 

 (Fig. 215). 



McBetk and Scales Formula (McBeth, I. G. and Scales, F. M.: The Destruction 



39 



