I 8 LABORATORY BACTERIOLOGY 



in suspension, the quantity and nature of sediment, and the 

 presence or absence of a membrane. The reaction of the 

 liquid should be taken and its consistence noted. The odor 

 should be determined. In agar cultures the extent of the 

 growth (feeble, moderate, or vigorous), its color, form, and 

 surface appearance (dull or glistening), should be observed. 

 The character of the growth in the condensation water should 

 also be noted. In stab cultures the appearance of the growth 

 both on the surface and along the needle track should be 

 described. In gelatin the absence or the presence and extent 

 of liquefaction should be noted in addition to the features 

 already referred to for the stab-agar cultures. (See Chester's 

 terminology, §§31 and 51.) 



27. Testing the reaction of liquid cultures. Place a small 

 piece of each of the red and blue htmus papers in a solid 

 «atch glass. With the platinum loop carefully place a drop 

 of the culture on each piece of the paper. After recording 

 the reaction produced, — neutral, acid, or alkaline, with the 

 degree, — cover the paper with a disinfectant (a solution of 

 corrosive sublimate i to looo). After it has acted for about 

 lo minutes, empty it with the paper into the waste jar and 

 wash the watch glass. 



28. To determine the viscidity, (a) Botiillon cultures. 

 Insert the platinum loop into the liquid and carefully with- 

 draw it. The approximate degree of viscidity may be deter- 

 mined by the extent of the adhesion of the liquid to the loop 

 and by the length of the threadlike filament drawn out. By 

 gently shaking the tube, a viscid sediment will rise up, appear- 

 ing as a somewhat twisted, tenacious cone with its apex 

 reaching to or near the surface. A friable sediment will break 

 up and become disseminated through the liquid upon agita- 

 tion, (i^) Agar and gelatin cultures. Touch the surface 

 growth with the end of the platinum needle, and if it is viscid, 

 a threadlike string will be drawn out. Note whether the 

 growth is pasty or friable. 



