CULTIVATION OF BACTK^l.\ 



61 



is then removed. With the aid of a platinum loop a drop or two of 

 melted agar is run along each side of the block to fill any angles between 



FIG. 36 



FIG. 37 





FIG. 36. Moist raised colonies with no visible structure, looking like a drop of water. 

 FIG. 37. Deep colonies, usually either light brown, gray or yellow in color, opaque, with little 

 marking. (Figs. 36-43 from Lehman and Neumann.) 



FIG. 38 



FIG. 39 



FIG. 40 



FIG. 38. The colonies very finely granular, with or w ithout twisted threads at borders. 

 FIG. 39. Colonies opaque in centre with lighter borders. The margin is coarsely granular. 

 FIG. 40. Colony in gelatin. The centre is coarsely granular in partly fluid gelatin. The borders, 

 are formed of wavy bands of threads. 



FIG. 41 



FIG. 42 



FIG. 43 



. ; - 



FIG. 41. Colonies circular in form, composed of radiating threads. 



FIG. 42. Colonies with opaque centres, with a thin border fringe. 



FIG. 43. Colony showing a network of threads which is thicker in centre. 



it and the cover-glass. After drying in the incubator for five minutes 

 it is placed over a hollow slide and sealed with paraffin. 



In using nutrient gelatin one must always remember not to allow it 

 to stay where the temperature is over 20 C., for if that happens the 



