Chemical and Physical Papers. 103 



salts, and 100 cc. of water give a combination which is equivalent 

 in results to the medium made from fresh liquid ox bile. 



Presumptive tests with this medium are not only more reliable 

 than those employing other media, but are easily made, requiring 

 the minimum skill in application. The lactose-bile medium is 

 especially valuable in testing wells, cisterns and filter plants. 



