26 PATHOGENIC BACTERIA 



made by bending the wire with the end of a small-pointed pair 

 of forceps into a complete circle, should be two millimeters 

 (about ^ inch), and in all cases it is to be sterilized by raising it 

 to a red heat in the flame before and after use (Fig. I). After 



Fig. 1. The 6se or platinum loop, the length of the wire and glass rod reduced. 



sterilization in the flame, the loop is inserted into the culture 

 tube, applied to the growing edge of the culture, withdrawn, 

 and immediately transferred to the drop of water on the cover- 

 glass, in which it is moved until slight turbidity appears; the 

 excess of the culture on the loop is now burnt off in the flame, 

 and the bacteria thoroughly distributed on the cover-glass by its 

 means, the drop being extended so as to cover an area of about 

 four millimeters in diameter. The cover glass is then seized at 

 the edge in a small pair of forceps, turned over, and applied to 

 the hollow ground slide so that the minute drop of fluid lies 

 over the center of the hollow space in the slide without coming 

 into contact with the latter; the gentlest pressure made around 

 the border of the cover-glass will then render the moist chamber 

 completely air-tight (Fig. 2). A moist chamber may be impro- 



Fig. 2. Section of hollow ground slide with cover-glass in situ, slightly re- 

 duced. 



vised, however, in a very effective manner on an ordinary flat 

 slide, as follows: Cut a piece of thick blotting-paper an inch 

 square, fold it, and cut away a small semi-circle from the center 

 of the folded border, open it out, wet it, and lay it on the slide; 



