CHAPTER XXI. 



Typhoid fever — Study of the organism concerned in its production. 

 Bacterium coK commune — Its resemblance to the bacillus of typhoid fever — 

 Its morphological, cultural, and jathogenic properties— Its diflFerentiation 

 from bacillus typhi dbdomiiiaiis. 



The organism, discovered by Eberth and by Gaffky, 

 generally recognized as the etiological factor in the pro- 

 duction of typhoid fever, may be described as follows: 



It is a bacillus about three times as long as it is 

 broad, with rounded ends. It may appear at one time 

 as very short ovals, at another time as long threads, 

 and both forms may occur together. Its breadth remains 



Fig. 67. Fig. 68. 





VT//-}/ 



Bacillus typhi abdominalis from Bacillus typhi abdominalis show- 



culture twenty-four hours old, on ing flagella stained by Lceffler's 



agar-agar. method. 



tolerably constant. Its morphology presents little that 

 will aid in its identification (see Fig. 67). It stains a 

 trifle less readily with the aniline dyes than do most of 

 the other organisms. It is very actively motile, and 

 when stained by the special method of lioeffler (see 



