368 



TYPHOID FEVER 



Neelsen carbol-fuchsin diluted with five parts of distilled water. 

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

 observation of the arrangement of the bacilli in the tissues, 

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

 few minutes, or in Loffler's 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 advantage (vide p. 101). In such preparations 

 the characteristic appearance to be looked for is the occurrence 

 of groups of bacilli lying between the cells of the tissue (Fig. 

 110). The individual bacilli are 2 /x to 4 /x long, with somewhat 



oval ends, and '5 /x in 

 thickness. Sometimes 

 filaments 8 /x to 10 /x 

 long may be observed, 

 though they are less 

 common than in cul- 

 tures. It is evident that 

 one of the bacilli may 

 frequently 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 Ap- 

 pearances of Cultures. 

 To grow the organism 

 artificially it is best to 

 isolate it from the spleen 



(for method, see p. 148), 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 

 visible 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 

 the agar are small, and appear as minute round points. Under a 

 low objective, the surface colonies are found to be very transparent 



FIG. 110. 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. 



