EXAMINATION OF WATER AND AIR. 251 



(Fig. 37). The stem must be sealed while the bulb is 

 still hot, or while a little water is being boiled in it, so 

 that a partial vacuum may exist in the bulb, in order 

 that the water may be sucked up into it when the 

 stem is broken. The inoculation of the media is now 

 made directly, or water from the tube is emptied into a 

 sterile bottle or test-tube, or the end of the Sternberg 

 bulb is sealed by heat. When water is to be obtained 

 from greater depths or from beneath the surface of 

 wells, more complicated forms of apparatus are neces- 

 sary. A good example is the one devised by Abbott, 



FIG. 38. 



Flask for counting colonies of bacteria. 



and made for him by Charles Leotz & Sons, of Phila- 

 delphia. It consists of a metal framework in which is 

 encased a bottle provided with a ground-glass stopper. 

 To the stopper a spring clamp is attached, and this in 

 turn is operated by a string, so that when the weighted 

 apparatus is allowed to sink into the stream the stopper 

 may be removed at any depth desired by simply pulling 

 on the string. When the bottle is full the stopper is 

 allowed to spring back into position by releasing the 

 spring. Before removing the water the neck of the 

 bottle should be sterilized by pouring a little of a 5 



