14 NUTRITION FACTORS IN YEAST AND BACTERIA 



yeast varied from 5.5 to 9 mm. with an average of about 

 7.5 mm. This activity compared favorably with that of 1% 

 peptone solutions. Extraction of the norit from the second 

 shaking failed to give any action on yeast or bacteria. Table V 

 gives in detail the results of these extraction experiments with 

 beef-heart infusions. 



An interpretation of these results shows that the growth- 

 stimulating substances are present in smaller amounts in beef- 

 heart infusions than in autolyzed yeast; and that they are more 

 easily adsorbed from the former than from the latter. This 

 adsorption is more complete, at least from beef-heart infusions, 

 with norit than with fullers earth. Baryta fails to extract any 

 active substance from the norit after adsorption, while glacial 

 acetic acid is ineffective on fullers earth. 



TABLE V. 



Effect of Shaking of Beef-Heart Infusions with Fullers 

 tiarth and Norit. 



Net Yeast Bac- 



No. FULLERS EARTH growth terial 



in mm. growth 



1. Beef-heart infusion 1 cc. (equiv. to 2/5 



gm. beef -heart) 12.0 -f -f 



2. Beef -heart infusion shaken with 50 gras. per 



liter, 1 cc 3.0* + -f 



2 (a) Beef -heart infusion shaken with 50 gins, per 



liter, 2 cc 3.5* -}- -f 



2 (b) Baryta extract of fullers earth (from 2) 



1 cc 1.0 + 



2 (c) Baryta extract of fullers earth (from 2) 



2 cc 1.0 -f 



3. Beef-heart infusion (nitrate from 2) shaken 



with 100 grams per liter, 1 cc 0. 



3 (a) Beef-heart infusion (nitrate from 2) shaken 



with 100 grams per liter, 2 cc 0. 



3 (b) Baryta extract of fullers earth (from 3) 



1 cc 1.0 + 



3 (c) Baryta extract of fullers earth (from 3) 



2 cc 1.0 + 



NORIT 



4. Beef-heart infusion shaken with 20 grams 



(2%) per liter, 1 cc 0. -f 



4 (a) Acetic acid extract from norit (from 4) 



1 cc 7.5* -f + 



5. Beef -heart infusion (nitrate from 4) shaken 



with 50 grams per liter, 1 cc 0. 



6 (a) Acetic acid extract of norit (from 5) 1 cc 0. 



Average result of several extraction!. 



