ISOLATION AND CULTURE CHARACTERS. 321 



wise, 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 or gall-bladder, 

 as it exists there in greater numbers than in the other 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 cautery to destroy all superficial contaminating 

 ortranisms. A small incision is 



made into the organ with a -^ «lt - ..^ ^r-J^ // 





sterile knife, a little of the pulp 



removed by a platinum needle, *^-»i* ^' ' ?> ' ^^^^ 'v'- 





and agar or gelatin plates are -i "K^J^^ ft^ ■*^._S 



\f' ^ ^ It ^*.» j^v^ \ ^ ^ ' 

 prepared, or successive strokes r-' 't *, A^^, _a '*■'*• V-'VA t 



made on agar tubes. In like ^ t , "^ «'**-' / ^J? 



manner the gall-bladder is '.' ^'^\*'J '% -^'S '^"i ^ 



seared and punctured and cul- ^ii-%i-' n^i^ \ } \ 7' 



tures made from the bile. On \-^ ^^I'P* "^^V-^ J" 



the agar media the growths are ■''"i.'^i ^4a ''ir^^ 



visible after twenty-four hours' ' -^.4. V 



incubation at 37° C. On agar fig. 114. — Typhoid bacilli; from ayoung 



culture on agar, showing some filamentous 

 plates the superficial colonies forms, stained with wealt carbol-fuchsin. 



appear as circular spots, dull ^ '°°°- 



white by reflected fight, bluish-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 be very transparent (requir- 

 ing 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 than the superficial colonies. 

 On making cover-glass preparations, the bacilli are found to 

 present the same microscopic appearances as are observed in 

 preparations from sohd organs, except that there may be a 

 greater number of the longer forms which may almost be 

 called filaments (Fig. 113). The same is true of films made 

 from young gelatin colonies. Sometimes the diversity in the 



