274 Development of a Standardised Agar Medium 



organism, B. dendroides. This organism spreads by active motility, and 

 the factors controHing its spread were found to be (1) the existence of a 

 surface film of water on the agar, and (2) the rate of multiplication pre- 

 vious to the drying of this film. A medium was developed on which this 

 rate of multiplication was greatly reduced and on which, consequently, 

 spreading is greatly restricted. 



4. Tests of the medium have shown that the results obtained with 

 it are uniform and can be reproduced in different batches of medium. 



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{Received July 2\st, 1922.) 



