APPEARANCES OF CULTURES 



357 



>taining solutions, e.g. with carbol-thionin-blue, or with Ziehl- 

 Xerlsen carbol-fuchsin diluted with five parts of distilled w r ater. 

 As a rule, decolorising is not necessary. For the proper 

 observation of the arrangement of the bacilli in the tissues, 

 paratlin sections should be stained in carbol-thionin-blue for a 

 few minutes, or in Loftier'* methylene-blue for one or two hours. 

 The bacilli take up the stain somewhat slowly, and as they are 

 also easily decolorised, the aniline-oil method of dehydration 

 may be used with ad- 

 vantage (vide p. 100). 

 In such preparations the 

 characteristic appearance 

 to IK- looked for is tilt- 

 occurrence of groups of 

 bacilli lying between the 

 cells of the tissue (Fig. 

 106). The individual 

 bacilli are 2 p to 4 //. 

 Ion;:, with somewhat 

 oval ends, and '5 \L in 

 thickness. Sometimes 

 filaments 8 JJL to IQ p 

 long may be observed, 

 though they are less 

 common than in cultures. 

 It] is evident that one 

 of the bacilli may fre- 

 quently in a section be 

 viewed endwise, in which 

 case the appearance will 

 be circular. This ap- 

 pearance accounts for some, at least, of the coccus-like forms 

 which have been described. The bacilli are decolorised by 

 Grant 'j method. 



Isolation and Appearances of Cultures. To grow the 

 organism artificially it is best to isolate it from the spleen (for 

 method, see p. 146) 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. Agar or gelatin plates or agar stroke 

 cultures may be employed. On the agar media the growths are 

 \Mble after twenty-four hours' incubation at 37 C. On agar 

 plates the superficial colonies are thin and film-like, circular or 

 slightly irregular at the margins, dull white by reflected light, 

 bluish-grey by transmitted light. Colonies in the substance of 



Fie. 106. A large clump of typhoid bacilli 

 in a spleen. The individual bacilli are only 

 seen at the periphery of the mass. (In 

 this spleen enormous numbers of typhoid 

 bacilli were shown by cultures to be present 

 in a practically pure condition.) 



Paraffin section ; stained with carbol-thionin 

 blue, x 500. 



