BACTERIOLOGY OF MILK 155 



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 to 

 take up in a small quantity of water all the bacteria held back by the filter. Then 

 plate out on lactose litmus agar and examine colonies which do not show any pink 

 coloration. The dysentery bacillus has about the same cultural characteristics as 

 the typhoid one, so that it is important to note motility. If from such a colony 

 you obtain an organism giving the cultural characteristics of B. typhosus, carry out 

 agglutination and preferably bacteriolytic tests as well. Some strains of typhoid, 

 especially when recently isolated from the body, do i\ot show agglutination. 



The Conradi Drigalski, the malachite-green, and various caffeine containing plat- 

 ing media have been highly recommended. 



Isolation of the Cholera Spirillum from Water 



The method proposed by Koch in 1893 does not seem to have been improved upon 

 by later investigators. To 100 c.c. of the suspected water add i% of peptone 

 and i % of salt. Incubate at 38C., and at intervals of eight, twelve, and eighteen 

 hours examine microscopically loopfuls taken from the surface of the liquid in the 

 flask. So soon as comma-shape organisms are observed, plate out on agar. The 

 colonies showing morphologically characteristic organisms should be tested as to 

 agglutination and bacteriolysis. Inasmuch as the true cholera spirillum shows a 

 marked cholera-red reaction it is well to inoculate a tube of peptone solution from 

 such a colony and add a drop of concentrated sulphuric acid after incubating for 

 eighteen hours. The rose-pink coloration is given by the cholera spirillum with the 

 acid alone the nitroso factor in the reaction being produced by the organism. 



BACTERIOLOGICAL EXAMINATION OF MILK 



A bacterial milk count is of comparatively little value as showing 

 whether a milk is dangerous or not. As a matter of fact, a milk which 

 contains several million of bacteria per c.c. might be less dangerous 

 than one containing only a few thousand, especially if in the latter 

 there were numerous liquefiers and gas producers present. There Js, 



