THE GROWTH AND APPEARANCES OF COLONIES 69 



the microscope should be of such size as to carry a culture 

 plate easily upon it. 



The second dilution or third plate is usually made use of 

 that one containing the colonies sufficiently isolated. 



These isolated ones should be sought for, and their appear- 

 ance well noticed. 



There may be two or three forms from the same germ, the 

 difference due to the greater or less amount of oxygen that they 

 have received, or the greater or less amount of space that they 

 have had to develop in. 



The microscopic picture varies greatly; now it is like the 

 gnarled roots of a tree, and now like bits of frosted glass; the 



Fig. 36. Microscopic appear- Fig. 37. Klatsch preparations, 



ances of colonies 



pictures are very characteristic, and the majority of bacteria 

 can be told thereby (Fig. 35). 



Impression or " Klatsch " Preparations. In order more 

 thoroughly to study a certain colony and to make a permanent 

 specimen of the same, we press a clean cover-glass upon the 

 particular colony, and it adheres to the glass. It can then be 

 stained or examined so. The Germans give the name of 

 " Klatsch' ' to such preparations. Many beautiful pictures can 

 be so obtained. 



Fishing. To obtain and examine the individual members of 

 a particular colony the process of fishing, as it is called, is 

 resorted to. 



