1923] 



JENNISON — POTATO BLACKLEG 27 





paper; (8) titrate, using phenolphthalein as an indicator; (9) deter- 

 mine reaction and adjust if necessary; (10) sterilize in autoclave at 

 15 pounds for 15 minutes. 



BEEF AGAR 



(1) Nutrient broth (steps 1-6) is brought to a boil; (2) while boil- 

 ing add 1 per cent "Bacto" agar, sifting it over the surface; (3) when 

 agar is completely dissolved, cool and clarify in usual manner; 

 (4) determine reaction and adjust if necessary; (5) filter; (6) steril- 

 ize in autoclave. 



GELATIN 



(1) To nutrient broth already prepared (steps 1-6), add 10 per 



cent "Bacto" gelatin and dissolve at a low temperature ( 60-70 °C.) ; 

 (2) determine reaction and adjust if necessary; (3) filter, tube, and 

 sterilize at 15 pounds for 15 minutes. 



DUNHAM'S SOLUTION 



Make a paste of 10 gms. peptone and 5 gms. salt in a small quantity 

 of water; then add sufficient water to make total used 1000 cc. 

 Heat in flowing steam for y 2 hour, then boil for 10 minutes over free 

 flame. Make up water lost by evaporation. Filter through paper and 

 tube. Sterilize in autoclave at 15 pounds for 15 minutes. 



CARBOHYDRATE BROTH 



(1) To nutrient broth already prepared (steps 1-6) add 1 per cent 

 by weight of the chemically pure carbohydrate; (2) determine and 

 record reaction; (3) filter, tube, and sterilize in autoclave at 15 

 pounds for 15 minutes. 



MILK 



The milk used was freshly drawn into a sterile bottle. After 

 standing about an hour it was centrifuged and the cream skimmed 

 off. Samples were titrated, using phenolphthalein as an indicator, 

 and the reaction was determined to be "+20". The reaction was 

 not adjusted. The medium was tubed promptly and sterilized by 

 exposing tubes in flowing steam for 20 minutes on 3 consecutive days. 



LITMUS MILK 



To part of the fresh milk (see above), was added 2 per cent by 

 volume of a saturated aqueous litmus solution (Merck's reagent, 1 gm. 

 to 15 cc. H 2 0). This medium was tubed immediately and sterilized by 

 exposure to flowing steam for 20 minutes on 3 consecutive days. Both 

 milk media were kept 4 or 5 days before being inoculated. 



RAW POTATO PLUGS 



A considerable number of raw potato plugs were prepared, observ- 

 ing all possible antiseptic precautions. The lot was kept several days 

 in order to insure the removal of any contaminations that might 

 appear. 



