BACILLUS TYPHOSUS. 415 



breadth remains tolerably constant. Its morphology 

 presents little that will aid in its identification. (See 

 Fig. 71.) It is actively motile, and when stained by 

 special methods, is seen to possess very delicate loco- 

 motive organs in the form of fine, hair-like flagella, 

 attached in large numbers to all parts of its surface. 

 (See Fig. 72.) These flagella are not seen in unstained 

 preparations, nor are they rendered visible by ordinary 

 methods of staining. (See methods for staining fla- 

 gella.) 



Owing to a tendency to retraction of its protoplasm 

 from the cell-envelope and the consequent production 

 of vacuoles in the bacilli, the staining of this organism 

 is frequently more or less irregular. At some points in 

 a single cell marked differences in the intensity of the 

 staining will be seen, and here and there areas quite free 

 from color can commonly be detected. These colorless 

 portions are often so sharply defined that they look as 

 if they had been punched out with a sharp instrument. 

 (See page 73.) 



It does not form spores. 



FIG. 73. 



Diagrammatic representation of retraction of protoplasm, with pro- 

 duction of pale points, in bacillus typhosus. 



GELATIN PLATES. Its growth, when seen in the 

 depths of the medium, presents nothing characteristic, 

 appearing simply as round or oval, finely granular 

 points. On the surface it develops as very superficial, 



