82 HISTORY AND CAUSE OF THE COCONUT BUD-EOT. 



This experiment was repeated with another lot of neutral-red agar, 

 believed to be the same as the first lot, with the exception of titrating 

 three degrees higher on the Fuller scale. Whatever the cause may have 

 been there was no change in the color of the medium from pink to 

 canary yellow. A moderate amount of pinkish growth appeared on 

 the surface, but otherwise there was no characteristic reaction. 

 This medium was made up in each case with 1 per cent agar flour, 

 beef bouillon made with distilled water, 2 per cent dextrose, and 

 enough neutral red to make a bright pink. 



In MacConkey's bile-salt agar (for full description see p. 83) con- 

 sisting of peptone, sodium taurocholate, lactose, and neutral red, 

 the canary-yellow color in the lower part of the medium was very 

 striking. 



According to Hunter,^ Kosenberger,^ and Moore and Revis,^ the 

 neutral-red reaction is characteristic of Bacillus coli and a few other 

 organisms. This reaction is thus useful in separating this group of 

 organisms from others. Moore and Revis have found that under 

 certain conditions the canary-yellow reaction does not always result. 

 In particular they found that in the presence of glucose the reaction 

 seldom occurred. Lactose was considered to be the best sugar to 

 use, and the result in MacConkey's bile-salt agar containing lactose 

 seems to verify this. It is stated by these authors that the canary- 

 yellow color is only transitory when resulting in glucose media. 



For a further test of the constancy of this canary-yellow reaction 

 experiments were made with agar media without sugar, with lactose, 

 with dextrose, with saccharose, and with glycerin. The six coconut 

 organisms and Bacillus coli were grown in these media in two different 

 experiments. Table XIV shows the results of these experiments 

 with B. coli and coconut No. 5. 



1 Hunter, William. The Diagnosis of the Presence of Bacillus Coli Communis by Means of Neutral Red. 

 British Medical Journal, Sept. 21, 1901, pp. 791-792. 



« Rosenberger, R. C. The Identification of the Colon Bacillus by Reactions Produced in Culture Media 

 Containing Neutral Red. Philadelphia Medical Journal, vol. 9, Mar. 8, 1902, pp. 446-449. 



3 Moore, Ernest W., and Revis, Cecil. The Neutral-Red Reaction for Bacillus Coli Commvmis. Journal 

 of Pathology and Bacteriology, vol. 10, 1904-5, pp. 97-104. 



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