ESSENTIALS OF BACTERIOLOGY. 



teria kills them and changes their shape to some extent, it is pre- 

 ferable to examine them when possible in their natural state. 



We obtain the bacteria for examination, either from liquid or 

 solid media. 



From Liquids. With a long platinum needle, the end of which 

 is bent into a loop, we obtain a small drop from the liquid con- 

 taining the bacteria, and place it on a cover-glass or slide ; 

 careful that no bubbles remain. 



Sterilize Instruments. Eight here we might say that it is 

 best to accustom one's self to passing all instruments, needles, 

 etc., through the flame before and after each procedure ; it in- 

 sures safety ; and once in the habit, it will be done automati- 

 cally. 



From Solid Media. With a straight-pointed platinum needle, 

 a small pinch of the medium is taken and rubbed upon a glass 

 slide, with a drop of sterilized water, or bouillon, and from this 

 a little taken on cover-glass, as before. 



FIG. 9. 



Platinum Needles. 



The cover-glass with its drop is now placed on the glass slide, 

 carefully pressing out all bubbles. Then a drop of cedar-oil is 

 laid on top of the cover-glass, and the oil immersion lens dipped 

 gently down into it as close as possible to the cover-glass, 

 the narrow blender shutting off the Abbe condenser, for this 

 being an unstained specimen, we want but little light. We now 

 apply the eye, and if not in focus, use the fine adjustment, or, 

 using the coarse, but always away from the object that is to- 

 wards us, since the distance between the specimen and the lens 



