THE METHODS OF CULTIVATING MICROBES 67 



Drop-cultures form ready means for studying the 

 complete life-history of any microbe. 



The methods for examining fluids and fresh tissues 

 are as follows: (1) blood, urine, saliva, pus, tears, 

 culture-fluids, and other liquids containing microbes, 

 are easily examined microscopically by placing a 

 drop of the liquid on a glass slide and covering it 

 with a thin cover-glass; (2) when microbes for 

 examination are growing on plates of nutrient 

 gelatine, a small portion of the culture should be 

 taken up on a sterilised platinum or glass needle 

 and placed in a drop of sterilised water on a glass 

 slide. After thinning, the preparation is covered 

 with a cover-glass and examined under low and 

 high powers ; (3) for the microscopical examination 

 of fresh tissues, they should be teased out with 

 sterilised needles in dilute glycerine or salt solution 

 (sterilised), then temporarily mounted, in either 

 liquid, on a glass slide and covered with a thin 

 cover-glass. If there is an excess of glycerine or salt 

 solution round the edges of the cover-glass, it must be 

 removed by placing small pieces of filter or blotting- 

 paper in contact, which will soon absorb the super- 

 fluous fluid, but the paper must not be left too long 

 or it will drain the fluid from under the cover-glass. 

 In the examination for micrococci and other small 

 microbes, the tissues should be first treated with 

 acetic acid, and then with a solution of potassium 

 hydroxide (potash), the object being to dissolve and 

 disintegrate fatty and albuminous globules which 

 might be mistaken for microbes. Alcohol and ether are 

 also useful agents for dissolving small globules of fat. 



