may show only normal flagella, only curly flagella, or mixed curly 

 and normal. Occasionally a flagellum may be part normal and 

 part curly in various arrangements. Most Proteus flagella, except 

 those of P. rettgeri, assume the normal shape in media above pH 

 7.5 and the curly shape in media below pH 6.5. At a pH between 

 6.5 and 7.5 the flagellation tends to be mixed normal and curly. 

 This pH sensitivity is not unique for Proteus but is also found to 

 a limited extent in Erwinia, Azotohacter, and Bacillus. 



In addition to the normal and curly shapes, coiled flagella 

 were observed to a variable extent in all species, absent in some 

 strains but common in others. In the Providence group, and in 

 some strains of P. morganii, a very few organisms showed the 

 semicoiled shape. The semicoiled flagella are very characteristic 

 having an exceptionally large amplitude in relation to the wave- 

 length. 



Flagellar Measurements 



The wavelengths and amphtudes of Proteus flagella were 

 measured to a great extent. In Table X are summarized the mean 

 wavelengths and amphtudes of the normal and curly flagella of 

 the sixty best flagellated strains. Studies were also made of the 

 effect of variation in culture medium, age of culture, etc. These 

 studies showed remarkably little variation in wavelength and 

 amplitude in different media and at different ages of culture. In 

 summarizing the statistical data it may be stated: statistically sig- 

 nificant variations are found in the mean strain wavelengths in- 

 dicating that a species in Proteus is not morphologicalh' homo- 

 geneous. The mean wavelengths of normal flagella of P. mirabilis, 

 P. vulgaris, and P. morganii do not differ significantlv but do 

 differ significantly from the mean wavelengths of P. morganii 

 (trehalose -(-), P. rettgeri, and the Providence group. The mean 

 spiral unit lengths 



S.U.L. := VWL^ + AmpV 



were not significantly different except for P. rettgeri which was 

 greater. Again P. rettgeri appears different from the others. The 

 curly flagella of all strains were of quite uniform wavelength, being 

 slightly greater for the Providence group. P. rettgeri showed so 

 few curly flagella that it could not be compared with the others. 



110 



