528 H. J. CONN, CHAIRMAN 



method was described by Kligler (1917) and has been reported 

 upon favorably from other sources. Although certain weak- 

 nesses in the technic have been pointed out it is given here as 

 a provisional method. The committee has not yet had an 

 opportunity to give it the investigation it needs and therefore 

 does not indorse the method. 



Prepare an agar like the standard peptone-beef-extract for- 

 mula but with 30 grams instead of 5 grams of peptone per liter, 

 and with a reaction between pH = 7.2 and pH = 7.6 (i.e., just 

 at the alkaline, or blue end of the sensitive range of brom thy- 

 mol blue). Sterilize this medium 5 cc. to the tube. Sterilize 

 separately a 0.1 per cent solution of basic lead acetate, and 

 after sterilization add 5 cc. to each tube of agar, when the agar 

 has cooled to about 50°C. Allow the tubes to cool in an upright 

 position, and incubate for a long enough period to be sure that 

 no contamination is present. Inoculate these tubes with the 

 organisms to be tested by stabbing with an inoculating needle. 

 Incubate at optimum temperature for from eighteen hours to a 

 few days according to the vigor of the culture. Hydrogen sul- 

 fide causes a blackening or browning of the medimn along the 

 hne of inoculation. 



KEFERENCES 



Atkins, K. N. 1920 A modification of the Gram stain. Jour. Bact. 5, 321-324. 



Committee on the Descriptive Chart 1917 Methods of pure culture study. 

 Jour. Bact. 3, 115-138. 



Committee on the Descriptive Chart 1920 Methods of pure culture study. 

 Revised. Jour. Bact. 5, 127-143. 



Conn, H. J., and Hucker, G. J. 1920 The use of agar slants in detecting fermen- 

 tation. Jour. Bact. 5, 433-435. 



Friebeb, W. 1921 Beitrage zur Frage der Indolbildung und der Indolreak- 

 tionen sowie zur Kcnntnis des Verhaltens indolnegative Bakterien. 

 Centbl. f. Bakterio!., 1, Abt., Grig., 87, 254-277. 



Hucker, G. J. 1922 Comparison of various methods of Gram staining (Prelimi- 

 nary Report). Abstr. Bact. 6, 2. 



Htjckeb, G. J., AND Wall, VV. A. 1922 The use of agar slants in detecting am- 

 monia production and its relation to the reduction of nitrates. Jour. 

 Bact. 7, 513-516. 



Kligler, I. J. 1917 A simple medium for the differentiation of members of the 

 typhoid-paratyphoid group. Am. Jour. Pub. Health. 7, 1042. 



ZiPFEL, H. 1912 Zur Kcnntnis der Indolreaktion. Centbl. f. Bakteriol., 1 abt., 

 Grig., 64, 65-SO. 



