3 oo 



TYPHOID FEVER. 



they are less common than in cultures. It is evident that 

 one of the short oval forms may frequently in a section 

 be viewed endwise, in which case the appearance will be 

 circular. This appearance accounts for some, at least, of 

 the coccus -like forms which have been described. The 

 bacilli are decolorised by Gram's method. 



Isolation and Appearances of Cultures. To grow the 

 organism artificially it is best to isolate it from the spleen, 

 as it exists there in greater numbers than in the other solid 

 organs, and may be the sole organism present even some 

 time after death. The spleen is removed whole, and a 

 portion of its capsule is seared with a hot piece of metal in 

 order that all superficial contaminating organisms may be 

 destroyed. A small incision is made into the organ with a 

 sterile knife, a little of the pulp removed by a platinum 

 needle, and agar or gelatine plates are prepared, or succes- 

 sive strokes made on agar tubes. On the agar media the 

 growths are visible after twenty-four hours' incubation at 



37C. On agar plates 

 the superficial colon- 

 ies appear as circular 



4. V l~ ***** ''/ / 'j*'***^ spots, dull white by 

 !R } Xf*^ \ reflected light, bluish- 



1 " i\ ** *j- i. xOs* ._>*ih 1 *. _^A i . , 



grey by transmitted 

 light. Colonies in 

 the substance of the 

 agar are small, and 

 appear as minute 

 round points. When 

 viewed under a low 

 objective, the surface 



__ __ colonies are found to 



FIG. 77. Typhoid bacilli ; from a young be very transparent 

 culture on agar, showing some filamentous (requirin^ a small dia- 

 phragm for their de- 

 finition), finely granu- 

 lar in appearance, and with a very coarsely crenated and 

 well-defined margin. The deep colonies are usually 



^Stained with weak carbol-fuchsin. 



