CHAPTER XXII. 



BACTERIACE^E: THE COLON, TYPHOID AND DYS- 

 ENTERY BACILLI. 



Bacillus Coli. This organism was probably observed by sev- 

 eral investigators previous to 1886 but it was either neglected or 

 its significance was misinterpreted. The first important study 

 of it was made by Escherich in that year, who discovered it in the 

 feces of healthy infants and obtained it alone on the aerobic gela- 

 tin plate cultures inoculated with this material. 



FIG. 130. Bacillus coll showing flagella. (From McFarland after Migula.} 



B. coli lives and grows in the intestinal tract of man and mam- 

 mals, and organisms closely resembling it have been found in the 

 intestinal canal of other vertebrates. It is discharged in large 

 numbers in the feces and some of these bacilli may continue their 

 growth in the external world for a time. The organism is 0.4 to 



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