APPENDIX 271 



and the final results should correspond to the acidity 

 recommended by the standard methods. What has been 

 said regarding the necessity of correcting for moisture in 

 gelatin applies with equal force to agar and for the same 

 reasons. 



NUTRIENT GELATIN AND AGAR 



Nutrient gelatin and agar shall be prepared as follows: 



Gelatin. Agar. 



,1. Boil 15 gm. thread agar in 500 c.c. 



water for half an hour and make 

 up weight to 500 gm. or digest for 

 IS minutes in the autoclav^e. Let 

 this cool to about 60° C. 



2. Infuse 500 gm. lean meat 24 Infuse 500 gm. lean meat 24 hours 

 hours with 1000 c.c. of dis- with 500 c.c. of distilled water in 

 tilled water in refrigerator. refrigerator. 



3. Make up any loss by evaporation. 



4. Strain infusion through cotton flannel. 



5. Weigh filtered infusion. 



6. Add I per cent Witte's pep- Add 2 per cent of Witte's pep- 

 tone and 10 per cent Gold tone. 



Label sheet gelatin on dry 

 basis. 



7. Warm on water bath, stirring till peptone and 

 gelatin are dissolved and not allowing the 

 temperature to rise above 60° C. 



8- To 500 gm. of the meat infusion 



add 500 c.c. of the 3 per cent 

 agar, keeping the temperature 

 below 60° C. 



9. Titrate, after boiling one minute to expel 



carbonic acid. 



10. Adjust reaction to -|-i.o per cent by adding 

 normal hydrochloric acid or sodium hydrate 

 as required. 



11. Heat over boiling water (or steam) bath for 

 40 minutes. 



12. Restore loss by evaporation. 



13. Readjust to +1.0 per cent if necessary and 

 boil 5 minutes over free flame, constantly 

 stirring. 



14. Make up loss by evaporation. 



