TYPHOID AND WATER 131 



corded and then that remaining after the CO2 has been absorbed is reported as 

 hydrogen.) 



4. Nonliquefaction of gelatin. 



5. Fermentation of lactose with gas production. 



6. Indol production. 



7. Reduction of nitrates to nitrites. 



To these may be added the acidifying and coagulation of litmus milk without 

 subsequent digestion of the casein. The production of gas and fluorescence in glu- 

 cose neutral red bouillon is also a very constant function of the colon bacillus. 

 B. coli aerogenes is similar to B. coli with the exception of nonmotility and production 

 of gas in saccharose media. B. coli anaerogenes is also similar to B. coli but does not 

 produce gas in glucose and lactose. 



NOTE. The reduction of neutral red with a greenish-yellow fluorescence is very 

 striking and has been suggested as a test for the colon bacillus. Many other organ- 

 isms, especially those of the hog cholera group, have this power. It is convenient, 

 however, to color glucose bouillon with about i% of a 1/2% solution of neutral red. 



On the plates made for the detection of colon bacillus may be found 

 certain organisms which have origin in fecal contamination. The more 

 important of these are those of the paratyphoid, cloaca and proteus 

 groups. In addition, the B. fecalis alkaligines has not rarely been 

 isolated. Among natural water bacteria there may be present either 

 the liquefying or the nonliquefying B. fluorescens. These colonies 

 have a yellowish-green fluorescence. 



Certain chromogenic cocci and bacilli are found in uncontaminated 

 waters as B. indicus or B. violaceus. From surface washings we obtain 

 certain soil bacteria as B. mycoides, B. subtilis, B. megatherium. One 

 of the higher bacteria which shows long threads, Cladothrix dichotoma, 

 is common, and is characterized by a brown halo around it's gelatin 

 plate colony. 



Isolation of the Typhoid Bacillus from Water. 



This is probably the most discouraging procedure which can be 

 taken up in a laboratory. Only the most recent reports of such isola- 

 tion from water supplies, which have been verified by immunity reac- 

 tions, can be accepted and of these the number of instances is exceed- 

 ingly small. Owing to the long period of incubation, the typhoid 

 organisms may have died out before the outbreak of an epidemic 

 suggests the examination of the water supply. 



There have been various methods proposed for the detection of the B. typhosus 

 in water. A method which would offer about as reasonable a chance of success as 

 any other would be to pass 2 or 3 liters of the water through a Berkefeld filter; then 



