'.04 



TYPHOID FEVER 



members have an effect on this sugar; in the ultimate differ- 

 entiation of the organisms immunity reactions are of essential 

 importance. 



The Bacillus Coli Communis. 



Bacillus Coli Communis. — Morphological Characters. — These 

 are best seen in young bouillon or agar cultures. The bacillus is 

 ordinarily from 2 to 4 yu. long and about -5 /x broad; longer 

 forms up. to 8 or 10 /u. are not infrequent (Fig. 104). It is 

 usually found to be motile, but the motility varies in different 

 strains and under different growth conditions in the same strain. 



The organism may stain 

 somewhat faintly with 

 watery dyes, but is 

 readily demonstrated 

 with carbol-fuchsin (1 

 of the Ziehl-Neelsen 

 stain in 20 of water); 

 it is Gram-negative. In 

 older cultures the bacil- 

 lary protoplasm may be 

 vacuolated and ballooned 

 at the ends. By appro- 

 priate staining b. coli 

 derived from cultures can 

 be shown to possess 

 flagella springing from 

 all round the organ- 

 ism, varying in number 

 and occasionally rather 

 short. 



Culture Reactions on Ordinary Media.— The following are 

 the appearances of the b. coli in the ordinary culture media :— 

 In bouillon,, it produces a uniform turbidity. In stab cultures 

 on peptone gelatin an abundant film-like growth takes place on 

 the surface, and there is a whitish or brownish-white line along 

 the stab without liquefaction of the gelatin. In sloped agar 

 tubes a somewhat dense, glistening, white or brownish-white 

 growth occurs along the stroke. On agar plates the surface 

 colonies are somewhat large and, it may be, irregular in outline, 

 but the deep colonies are smaller and lenticular in shape, and 

 under a low power of the microscope appear rather dense to 

 transmitted light. A similar growth occurs on blood serum. 

 On potatoes, in forty-eight hours, there is a distinct film of 



Fio. 104.— Bacillus coli communis. Film 

 preparation from a young culture on agar. 

 Stained with weak carbol-fuchsin. x 1000. 



