PATHOGENIC BACTERIA. 313 



some lesion of the intestine existed simultaneously, but in most 

 cases without having produced much apparent damage to the or- 

 gans invaded. The Bacillus coH communis frequently occurs 

 in mixed infections, as in wounds, inflammations and abscesses. 

 It is often found in the peritoneum in peritonitis, in the pus in 

 appendicitis, and in the urine in cystitis; it frequently occurs 

 in the interior of gall-stones with whose formation it may be 

 connected,* as first pointed out by Welch. 



There is a large number of more or less closely related 

 organisms which go by the name of the '^ colon group." The 

 limits of the colon group are extremely ill defined. 



Detection of Bacillus coli communis in Water. — To each of a number of 

 fermentation-tubes containing i per cent, dextrose-bouillon add some of the 

 suspected water (o.i to i c.c. or more). Place in the incubator. Each day 

 mark the amount of gas that has formed in the closed arm. After two days 

 B. coli communis should render the bouillon strongly acid and produce about 

 50 per cent, of gas (30 to 70 per cent, according to different writers). The, 

 gas is approximately H two parts, and COj one part (see page 120). From 

 tubes showing these characters plates may be made and the usual tests for 

 the colon bacillus applied. f (See Part IV.) Stokes recommends adding the 

 water to fermentation tubes containing t per cent, lactose-bouillon and neutral 

 red (10 c.c. of a 3 per cent, solution of neutral red to a liter of bouillon); if 

 the colon bacillus is present, 30 per cent, to 50 per cent, of gas is formed (con- 

 sisting of one part of carbon dioxide and two parts of hydrogen), and the neu- 

 tral red in the closed arm changes to a yellow color. { 



Paracolon or paratyphoid bacilli are the names applied to certain members 

 of the colon group which have recently been shown to be pathogenic to man. 

 They may produce clinical symptoms resembling typhoid fever of a mild and 

 atypical form. The affection is rarely fatal. Probably they may occur with 

 typhoid fever in mixed and secondary infections. Characteristic lesions have 

 not yet been observed. The bacilli have been found in the blood, spleen, 

 liver, gall-bladder and urine. Like typhoid and colon bacilli they are motile, 

 have flagella, are not stained by Gram's method and do not Uquefy gelatin. 

 They ferment dextrose and maltose, producing acid and gas. They do not 

 ferment lactose. Milk at first becomes acid, later it becomes alkaline, and 

 is not coagulated. On potato a slight visible growth occurs. Media contain- 



* Lartigau. Journal American Medical Association. April 12, 1902. 

 t Theobald Smith. American Journal Medical Sciences. Vol. CX. 1895. 

 j Journal of Infectious Diseases. I. 341. 

 27 



