PATHOGENIC BACTERIA. 385 



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.* 



Jackson t advises the use of bile as an inhibiting agent for the bacteria other 

 than the intestinal bacteria found in water, The restraining action of the bile 

 is due to the colic acid radical of the bile. Jackson rfecommends that undiluted 

 ox-bile be employed. This is sterilized as soon as it is drawn, and may then 

 be kept in stock. When used it should be decanted or filtered, and one per cent, 

 of lactose previously dissolved in a small amount of water should be added. 

 It should then be distributed into fermentation tubes 140 mm. long by 15 mm. 

 in diameter having an elongated bulb 38 mm. in the shortest diameter. Instead 

 of fresh bile, no grams of dried bile and 10 grams of lactose dissolved in i hter 

 of distilled water may be employed. 



Swint recommends this medium particularly for sewage and for badly 

 contaminated water. 



The following scheme for the detection of B. coli in water has been recom- 

 mended by Longley and Warren. | 



Preliminary incubation in dextrose-broth fermentation tubes at 40° C. for 24 

 hours. Those showing gas are to be plated on htmus-lactose-agar. No note 

 need be made of the reaction nor of the amount of gas. The above plates are 

 to be incubated at 40° C. for 18 or 24 hours, and inoculations made on agar 

 slants from any red colonies that may be found. The agar slants shall be 

 incubated at 40° C. for 24 hours, and further tests made in dextrose-broth fer- 

 mentation tubes. Tubes developing no gas are noted as negative. Milk 

 tubes should also be inoculated from the agar slants and incubated at 40° C. 

 for two days, and examined for coagulation both days. Failure to coagulate 

 or digestion of casein after coagulation are to be regarded as negative. Culti- 

 vation for two days at 40° C. in nitrate-broth and testing for the presence of 

 nitrites at end of this time. The presence of nitrites is regarded as positive. 

 Cultures from the slant agar in peptone broth are incubated for 3 days at 

 40° C. and then tested for the presence of indol. The presence of indol is regarded 

 as positive. The above statement is a, somewhat condensed statement of 

 Longley and Warren's scheme. 



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 chnical symptoms resembhng typhoid fever of a mild and 

 atypical form, but Wells and Scott || found that there is litde to distinguish the 

 pathological lesions produced by the paracolon bacillus from other septicemias. 

 The intestinal lesions are quite variable, but there are no changes in the Peyer's 

 plaques or solitary follicles. The intestinal glands are little or not at all affected. 

 The ulcers of the intestines are not always present and when they are they 

 differ from tiiose found in typhoid fever. Probably they may occur with typhoid 

 fever in mixed and secondary infections. Characteristic lesions have not yet 

 been observed. The most constant change is splenic enlargement. The 

 affection is rarely fatal. The bacilU have been found in the blood, spleen, 

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

 have flagella, are not stained by Gram's method and do not hquefy 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- 



*Journal of Infectious Diseases. I. 341- 



f Journal Infect. Diseases. Supplement No. 3. May, 1907. pp. 30-32. 



tibid. pp. 32-38- 



%Journ. Infect. Dis. Vol. IV. 1907, pp. 397-415- 



WJourn. Infect. Dis. Vol. I. 1904. pp. 72-90. 



25 



