180 EXAMINING AIR, SOIL, WATER, AND FLUIDS FOR BACTERIA 



upper portion alone developing colonies. These are counted in the 

 usual manner. 



Modifications of the above method have been introduced by Ficker, 

 who uses glass powder as the filter mass, and by Frankland, who 

 uses sterile powdered sugar. 



Sedgwick and Tucker have modified the filtering device by pro- 

 viding at the upper end an expanded portion ruled outside in equal 

 squares. After aspiration of the air, gelatin is poured directly into the 

 tube. As soon as the sugar powder loaded with the air bacteria is 

 dissolved the tube is rolled on ice and becomes an Esmarch roll-tube. 

 This method avoids the transfer of the filter material into a separate 

 plate or tube. 



Bacteriologic Examination of Water. Collection of Water. The 

 collection of water differs according to the source from which it is 

 obtained. Two factors must be particularly considered: (1) Care 

 must be exercised that the water running into a sterile flask does 

 not wash into it bacteria which may have been on the outside of 

 the mouth of the vessel. The risk can easily be avoided by sterilizing 

 the flasks in the dry air sterilizer and wrapping them in paper which 

 is not removed until the actual moment of use. (2) Care must be 

 taken that water coming from a faucet does not collect from the 

 mouth of the latter bacteria which may have been deposited here by 

 some means other than the water itself. 



Operating and dressing rooms in hospitals are now frequently 

 provided with hot and cold sterile water, which must be examined 

 from time to time. In the bacteriologic examination of such water 

 the author has used the following method in order to exclude the 

 possibility of contamination from outside sources. A 150 c.c. beaker 

 is filled with 95 per cent, carbolic acid and held so that the mouth 

 of the faucet dips into the acid. After the latter has acted for several 

 minutes the beaker is removed and replaced by one containing hot 

 sterile water. This removes the carbolic acid. The faucet is next 

 opened and the water allowed to flow for several minutes. A sterile 

 flask is then partially filled and immediately closed with a cotton plug. 



When water has to be collected from a river, a large water tank, or 

 a pond, it is desirable to obtain the specimen at some distance from 

 the shore or wall of the tank. This can be accomplished by fastening 

 a string to a sterile flask containing lead shot, and throwing the 

 vessel out into the water. When filled it is rapidly withdrawn, and 

 after a little water has been poured out the flask is closed with a 

 sterile cotton plug. For obtaining water from a particular depth of a 

 body of water, special apparatuses have been constructed by Esmarch 

 and by Roux. Esmarch's device consists of a bottle with a rubber 

 cap and weight. It is lowered on a line to a definite depth, the 

 rubber cap is opened by a string attached to it, the bottle is filled, 

 the rubber cap closed again automatically, and the apparatus is 

 pulled up to the surface. 



