128 BIOLOGY AND TECHNIQUE 



2. Weigh with containing vessel. 



3. Heat over free flame until agar is dissolved, thirty to forty-five 

 minutes. (Great care should be exercised in determining that agar is 

 completely in solution.) 



4. Determine weight and make up loss by evaporation. 



5. Determine volume, titrate, and adjust to desired reaction. 



6. Cool to 60° C. 



7. Add whites of two eggs and stir thoroughly. 



8. Heat in Arnold steriUzer thirty minutes, stir, and reheat fifteen 

 minutes. 



9. Weigh and make up loss by evaporation. 



10. Determine volume, titrate, and correct reaction if necessary.^ 



11. Heat for five minutes, if reaction is corrected. 



12. Filter through cotton, tube, and sterilize. 



Meat-Infusion Agar.^—{A) 1. Infuse 500 gms. lean meat twelve to 

 twenty-four hours in 500 c.c. of distilled water in refrigerator. 



2. Strain through wet cotton flannel or wet cheese-cloth, and make 

 up volume to 500 c.c. 



3. Add 10 gms. of Witte's pepton and 5 gms. of common salt. 



4. Weigh solution and containing vessel. 



5. Warm over free flame or water bath till pepton and salt are dis- 

 solved, not allowing temperature to rise above 50° C. 



6. Determine volume, titrate, and neutralize. 



(B) 7. Add 15 gms. of thread agar to 600 c.c. of distilled water and 

 boil over free flame for thirty to forty-five minutes, watching and stirring 

 constantly till agar is completely dissolved. This will lose weight by 

 evaporation; final weight should be 515 gms. 



8. Cool this to about 60° C. 



(C) 9. Then to the solution A of meat infusion (at 50° C.) add the 

 solution B of agar (at 60° C). 



10. Heat for thirty minutes in Arnold sterilizer. Shake or stir 

 thoroughly, and heat fifteen minutes more. Adjust weight by adding 

 water. 



11. Determine volume, titrate, and adjust reaction to plus one per 

 cent acid or any desired reaction. 



12. Boil for two minutes over free flame, constantly stirring. 



■ While titrating, care should be taken that medium does not solidify along sides 

 of vessel. Agar may be made more quickly and successfully in autoclave. 



2 Glycerin agar is made by adding 6 per cent of C. P. glycerin to meat-extract 

 or meat-infusion agax. 



