cultures but only polar flagella in older cultures. This phenomenon 

 has not been observed in other bacterial genera. 



The chemical composition of the medium may greatly influence 

 the flagellation. Of greatest importance perhaps is the pH. A low 

 pH often has a distinctly deleterious effect on flagella. Ferment- 

 able carbohydrates should be omitted as much as possible and 

 only added to the medium if necessary for growth. Phosphates 

 appear to favor flagellation and the author routinely adds 0.1% 

 potassium phosphate to his media. As a rule liquid media give 

 better flagellation than soHd media but sometimes the reverse 

 seems to be true. For technical reasons, related to the staining 

 procedure, the liquid medium used should be perfectly clear prior 

 to inoculation. Any agar in the medium interferes with staining 

 of the flagella. Satisfactory flagella stains may be made from 

 thioglycollate cultures but better slides are obtained if the agar is 

 omitted. 



Bacterial Motility 



It is a good rule to examine the culture by moist preparation 

 prior to staining. A motile culture should always show presence 

 of flagella; if not, the staining technique is faulty. An apparently 

 nonmotile culture may show presence of flagella for several reasons. 

 The flagella may be in the "paralyzed" state; changes may have 

 occurred in the medium, such as low pH, which have damaged 

 the flagella; or the flagella may simply have ceased to function 

 from various causes. Bacteria with flagella of the curly type are 

 sometimes very poorly motile, and those with straight flagella are 

 comparatively nonmotile. Another reason for making a moist 

 preparation is that the nature of the motion indicates the nature 

 of the flagellation. A single polar flagellum moves the soma rapidly 

 and linearly without much, if any, wiggle. Peritrichous flagella 

 move the bacteria with a characteristic wiggle. With a little ex- 

 perience polar and peritrichous flagellation are recognized with 

 considerable accuracy. In a detailed study of the flagellation of 

 the genus Chromobocterium, moist preparations of several strains 

 showed linear motion characteristic of polar flagellation. However, 

 the flagella stains showed only occasional lateral flagella which 

 could not account for the motion observed. By modifying the stain 



2 



