536 H. J. SEARS AND LULU L. CASE 



When colonies did appear on the latter plates their number was 

 always small as compared with that on the plates made from the 

 milk emulsion. The following is the result of one of several such 

 tests. An emulsion was made in 1-100 sterile milk and 1 cc. 

 of this emulsion mixed with 9 cc. of sterile water and 9 cc. of 

 sterile 1-100 milk respectively. Plates made from the two 

 last mixtures gave: 



Water (5) (3) (2) 



1-100 milk (89) (69^ 



The conclusions reached in this investigation are : 



1. The present standard agar is not in itself a favorable me- 

 dium for the growth of certain types of bacteria occurring in milk. 



2. The small quantity of milk added to the medium in plat- 

 ing 1 cc. of a 1-100 dilution supplies the deficiency, but the 

 amount added in plating the higher dilution does not do so. 



3. More consistent results are obtained if the dilutions of the 

 sample higher than 1-100 are made in sterile 1-100 milk instead 

 of in sterile water. 



