V. METHODS EMPLOYED IN THE ROUTINE 

 EXAMINATION OF FECES 



No phase of bacteriology has been more seriously handicapped by 

 the lack of adequate methods than the study of intestinal micro- 

 organisms. The most recent contribution is the work of Morris, Porter 

 and Meyer (1919), who advocate the technique employed by them in 

 their bacteriological examinations of children's stools. While these 

 methods may be of considerable value in the hands of trained technicians, 

 and for certain purposes, they have not appeared practical and suffi- 

 ciently direct to be of material help in the present investigation. It has 

 been our aim to employ the simplest technique that is consistent with our 

 purpose, namely to determine at frequent intervals the relative numbers 

 of B. acidophilus-like bacteria as compared with the total of all other 

 organisms, and to follow the progress of gas-producing organisms as 

 they increase or decrease in numbers in the fecal material examined. 

 The following methods were adopted early in this work and have con- 

 stituted a large part of the daily routine examinations. They are pre- 

 sented at some length here because they have proven themselves prac- 

 tical and in a high degree satisfactory. 



THE USE OF WHEY AGAR PLATES 



At the outset 1 per cent glucose agar was employed for plating, etc. 

 This was soon discarded in favor of whey agar which by a series of 

 comparative tests was found to be superior in every way to the other 

 media under consideration. Many difficulties were at first encountered, 

 however, in the preparation of clear whey from skimmed milk. These 

 difficulties were eliminated as soon as the following method was 

 perfected. 



The skimmed milk is heated to 80 to 90° C, and five cubic centimeters 

 removed to a test tube; while the test sample is still hot it is treated 

 with 10 per cent solution of hydrochloric acid drop by drop until com- 

 plete coagulation takes place. This is repeated two or three times. 

 The calculated amount of acid required to coagulate all of the milk i^ 

 thoroughly mixed with the milk, the temperature of which is still 80 

 to 90°, and the casein allowed to settle. This is followed by filtration. 



