482 APPLICATION OF METHODS OF BACTERIOLOGY 



ably constant. Its . morphology presents little that will 

 aid in its identification. (See Fig. 84.) It is actively motile, 

 and when stained by special methods, is seen to possess very 

 delicate locomotive organs in the form of fine, hair-like 

 flagella, attached in large numbers to all parts of its surface. 

 (See Fig. 85.) These flagella are not seen in unstained 

 preparations, nor are they rendered visible by ordinary 

 methods of staining. (See methods for staining flagella.) 



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 



Fig. 86 



Diagrammatic representation of retraction of protoplasm^ with production 

 of pale points, in bacillus typhosus. 



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 Fig. 86.) 



It does not form spores. 



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, blue-white colonies, 

 with irregular borders. They are a little denser at the 



