2 BULLETIISr 361, U. S. DEPAETMENT OF AGEICULTUEE. 



of the sediment test they never had a means of quickly determining 

 the exact amount. It has also been a fact long and f aiiiy well estab- 

 lished that milk contaming sediment or visible dirt, such as manure, 

 hair, etc., was produced under insanitary conditions, but when these 

 ingredients were not present in the milk no field inspector could 

 determine its purity. 



Upon the adoption of the sediment test as a means of detecting 

 insanitary milk at the milk-receiving stations, the producers un- 

 doubtedly began to use methods calculated to remove the visible 

 dirt. Such methods have been resorted to as straining the milk 

 through cotton, cheesecloth, and Canton flannel to prevent the 

 detection of visible dirt at the station by the field inspector. These 

 metliods have so changed the value of the sediment test as a means 

 of judging pure milk that when no sediment or visible dirt can be 

 detected it is often almost impossible to state whether the milk is 

 produced under sanitary conditions or not. In order to determine 

 whether the sediment test could be wholly relied upon as a means 

 of detecting insanitary milk at milk-receiving stations, an experiment 

 was conducted with this purpose in view. 



OBJECT OF THE WORK. 



The object of this experiment was to prove whether milk contain- 

 ing little or no visible dirt, as often occurs when filtered through 

 certain substances by gravity, v/as free from a large number of bac- 

 teria. It was decided that by comparing the bacterial count with 

 the sediment test (also when milk was filtered through various 

 utensils) certain information could be obtained regarding this points 



OUTLINE OF EXPERIMENT. 



Briefly, the experiment was conducted as follows: 

 Three of what we considered the most practical sediment-test 

 apparatuses were used, namely, the Gerber, the Wizzard, and the 

 Lorenz. The Gerber apparatus was selected because it represents 

 a gravity method. The average length of time required for one 

 pint of milk to pass through the disk by this method was 15 minutes. 

 The Wizzard was selected as a pressure type which could be easily car- 

 ried for field work and attached to the milk bottle without removing 

 the milk. By this method the time required for the milk to pass 

 through the disk was about two minutes; its disadvantage was that 

 when the pressure was apphed there was no means of holding the 

 apparatus securely to the bottle. The Lorenz apparatus was se- 

 lected as a pressure type in which the milk is placed in the metal 

 container and the pressure applied. The time required by this 



