320 



TYPHOID FEVER. 



in a section be viewed endwise, in which case the appear- 

 ance 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 

 TT\ is seared with a 



.Xflfl^^^B^^EB \ 



cautery to destroy all 

 superficial contami- 

 nating organisms. 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 successive strokes 

 made on agar tubes. 

 On the agar media 

 FIG. 85. Typhoid bacilli; from a young the growths are 

 culture on agar, showing some filamentous yisible after twemy _ 



Stained with weak carbol-fuchsin. x 1000. four hours' incuba- 



tion at 37 C. On 



agar plates the superficial colonies appear as circular spots, 

 dull white by reflected light, bluish-gray 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 be very 

 transparent (requiring a small diaphragm for their definition), 

 finely granular in appearance, and with a very coarsely 

 crenated and well-defined margin. The deep colonies are 

 usually spherical, sometimes lenticular in shape, and are 

 smooth or finely granular on the surface, and more opaque 



