BACTERIOLOGICAL GRADE AGAR, GELATIN, AND PEPTONES 69 



to the following requirements as set forth in the Military Medical Purchase Descrip- 

 tion, ASMPA 1-212-000, dated 14 September 1953: 



"A 12 per cent solution in distilled water, after autoclaving for 15 minutes at 

 121 C, shall be clear and free of gross suspended particles. After solidifying, it shall 

 melt over a range of from 30 to 36 C. 



"It shall be free of fermentable carbohydrate when tested under the following 

 conditions: 



"Prepare a medium of 4 per cent Gelatin and 0.3 per cent NaCl with sufficient 

 phenolsulphonthalein added to give a readable color, tube in Durham fermentation 

 tubes and autoclave 15 minutes at 121 C. Inoculate with a loop of a 24-hour culture 

 of Escherichia coli. Neither acid nor visible gas shall be produced in 48 hours incuba- 

 tion at 37 C." 



PAPAIC DIGEST OF SOYBEAN MEAL 



A soluble nutrient material prepared by the action of the enzyme papain on soybean 

 meal followed by suitable purification and concentration. It meets the specifications 

 under Pancreatic Digest of Casein, except that it shows substantial amounts of reduc- 

 ing sugars. It contains fermentable carbohydrates and gives positive tests for 

 indole, acetylmethylcarbinol, and sulfide upon inoculation and incubation with the 

 specified organisms. 



(These specifications are essentially those contained in U.S. P. XV, page 1026, 

 except for changes in wording.) 



PEPTIC DIGEST OF ANIMAL TISSUE (A BACTERIOLOGICAL PEPTONE)^ 



"A tan powder, having a characteristic, but not putrescent, odor. Soluble in 

 water; insoluble in alcohol and in ether. An autoclaved solution (2 in 100) is clear 

 and is neutral or nearly so in its reaction. 



"Degree of digestion. Dissolve 1 Gm. in 10 ml. of water, and use this solution for 

 the following tests: 

 " (a) Overlay 1 ml. of the digest solution with 0.5 ml. of a solution of 1 ml. of glacial 



acetic acid in 10 ml. of diluted alcohol: no ring or precipitate forms at the junction 



of the two liquids, and on shaking, no turbidity results, indicating the absence of 



undigested protein. 

 "(6) Mix 1 ml. of the digest solution with 4 ml. of saturated zinc sulfate: a small 



amount of precipitate is formed, indicating the presence of proteoses. Retain the 



filtrate. 

 " (c) To 1 ml. of the filtrate from the preceding test add 4 drops of bromine T.S.: the 



light yellow color changes to a red-brown, indicating the presence of tryptophane. 



"Nitrogen content, loss on drying, residue on ignition, and nitrite. Proceed as 

 directed under Pancreatic Digest of Casein. 



"Microbial content. Dissolve 1 Gm. in 10 ml. of water. Spread 0.01 ml. on one 

 square centimeter of a glass slide. Stain by the Gram method, and examine with an 

 oil-immersion lens: not more than a total of 50 microorganisms, or clumps, are visible 

 in 10 consecutive fields. 



"Bacteriologic test. It meets the following tests for bacteria-nutrient properties. 

 Prepare media of the following compositions : 



" (a) 2 % of peptone and sufficient phenol red T.S. to give a perceptible color in water 

 " (6) 0.1 % of peptone in water 



1 Quoted from U.S. P. XV, pp. 1024-1027. 



