136 PRACTICAL BACTERIOLOGY. 



is the best, but because it is easily obtained. The 

 following is Loffler's method of staining flagella. 

 The surface of some agar -agar, -which has been 

 allowed to solidify obliquely in a test-tube, is rubbed 

 gently with a minute quantity of material taken 

 from a fairly young culture of the hay bacillus. 

 It is most important to spread this material out 

 as evenly as possible, and also to avoid injuring 

 the surface of the agar-agar, for in that case small 

 portions of the nutrient material are sure to get con- 

 veyed on to the preparations which are made later 

 on, and which are then completely spoiled. The cul- 

 ture is next placed in the incubator, and is kept for 

 about five hours at a temperature of about 35° C. 

 Division takes place very rapidly at this temperature, 

 about every twenty minutes; hence in about five hours 

 the whole surface of the asrar-agar is covered with a 

 thin layer of young bacilli, which are scarcely visible 

 to the naked eye. A minute trace of this layer ' is 

 then introduced into the hanging drop, where it is 

 examined with the microscope, in order to make sure 

 that the movements of the bacilli have not ceased. 

 This sometimes occurs, although the cause of their 

 cessation is not yet fully understood. 



If, then, the bacteria show continuous movements, 

 we rnix a second portion of the film very carefully and 

 quickly with a drop of ordinary tap water upon a 

 slide, rubbing the material as little as possible against 



