CHAPTEE XII. 



ORGANISMS EESEMBLING THE BACILLUS TYPHOSUS. 

 Bacillus Coli Communis (Bacillus of Escherich). 



THIS organism, when first discovered by Emmerich in 

 1885, was believed to be the cause of Asiatic cBoTeraT^rjut 

 one year later scherich_demonstrated that it was found in 

 the fecal discharges of healthy persons and animals and in 

 the water and soil contaminated with their discharges. The 

 exact identity of this bacillus has ever since been the subject 

 of much discussion and controversy. It has been described 

 as a non-virulent variety of the typhoid bacillus ; and as a 

 germ closely allied to the typhoid bacillus. It has also been 

 stated that the typhoid bacillus was really an involution-form 

 of the colon bacillus. 



The colon bacillus very closely resembles the typhoid 

 bacillus in its morphology and biology: 



It is a short, thick rod, with rounded ends, measuring from 

 1 p. to 3 fj. in length, and from 4 // to 7 fi in width (Fig. 129). 

 Oval forms and thread forms are also met with in culture. 

 It stains like Bacillus typhosus, and occasionally exhibits 

 unstained portions resembling spores, but it does not sporu- 

 late. It has from eight to ten terminal and lateral flagella 

 and is actively motile. It is a facultative anaerobe, and 

 grows readily on all culture-media at either the room or body 

 temperature. 



The colonies on the gelatin plate are a little larger than 

 those of the typhoid bacillus and they appear earlier. The 

 superficial colonies are small and leaf-shaped. The deep 

 colonies are yellowish-brown in color, round, and finely 

 granular. The medium is not liquefied. 



In gelatin stab cultures a nail growth is formed without 



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