TECHNIC BACTERIOLOGICAL EXAMINATION OF SOILS. 



281 



ounce bottles to which aliquots of soil were added and to the extra bottle 

 that was prepared for a blank check. In each case the cotton plug and lip 

 of the bottle is flamed just before the bottle is opened for the addition of the 

 water. Now bring up the oven containing the fifty-five eight ounce bottles, 

 take the sterile 100 ec. graduated cylinder, flame the cotton plug, remove it, 

 flame the mouth of the cylinder and by means of the graduated cylinder 

 place 90 ce. of sterile water in each bottle. The cotton plug closing each of 

 the bottles is flamed just before the bottle is filled. The eight ounce bottles 

 are arranged in five rows each eleven bottles long, running lengthwise of the 

 bench. 



'^tittlL 



Plate II. 

 Adding of sterile water to soils and dilution bottles. 



The bottles containing the water and soil are set out in a row in front of 

 the other bottles, (Plate II). The rubber stoppers that have been steaming 

 in the double boiler are put in the bottles containing soil and water in place 

 of the cotton plugs. Work from left to right always as it is easier and such 

 a system prevents mistakes. The first two of the bottles in the front row 

 are grasped, one in each hand, in such a way that the index finger presses 

 down on the stoppers. The bottles are lifted up from the laboratory table, 

 the hands and arms are turned so that tlie bottles are upside down, and the 

 bottles are shaken vigorously for fifteen seconds and then placed back on 

 the table. The next two bottles are picked up in the same manner, inverted, 

 shaken for fifteen seconds and then placed back on the table. This is con- 

 tinued until each bottle has been shaken 10 fifteen second periods. 



