436 S. HENRY AYERS AND PHILIP RUPP 



this medium and only occasionally were colonies of non-gas 

 forming organisms observed which resembled those of organisms 

 of the colon-aerogenes group. 



Certain molds may develop on this medium which first appear 

 as minute red colonies, but later they show the typical appear- 

 ance of mold colonies. 



It is not claimed that the medium is perfect in its selective 

 action, that is to say, that it allows only the growth of organisms 

 of the colon-aerogenes group. Probably a medium perfect in 

 this respect can never be obtained. Every colony which de- 

 velops can not be considered a gas former, but from the appear- 

 ance of the colonies it is believed an accurate direct colon count 

 can be obtained. 



The flora of the material under examination may influence 

 the accuracy of the count and the value of this simple synthetic 

 medium. It has proven of great value in the determination of 

 the colon count of milk and undoubtedly it can be used in the 

 examination of other foods. A few results indicate that the me- 

 dium should be particularly useful in the direct enumeration of 

 organisms of the colon-aerogenes group in water. 



This synthetic medium can probably be improved and it is 

 hoped that it will be given a thorough trial in different laboratories 

 and its defects brought to the attention of the writers. 



ADVANTAGES OF THE MEDIUM 



1. Apparent accuracy in the direct enumeration of bacteria 

 of the colon-aerogenes group. 



2. Constancy of composition. 



3. Simplicity of preparation. 



4. Cheapness. 



REFERENCE 



De Bord, George C. 1917 The fuchsin aldehyde reaction on endo medium. 

 Jour. Bact, 2, 309-314. 



