720 A MANUAL OF BACTERIOLOGY 



litre. After the precipitate of aluminium hydrate has formed, 

 the vessel is well shaken to mix its contents, and the mixture is 

 centrifuged for fifteen minutes at 2,000 revolutions per minute. 

 The clear, supernatant fluid is then syphoned or poured carefully 

 off from the precipitate, and the mass of precipitate in the conical 

 extremity of the tube stirred up with the little fluid (0-5 to 1 c.c.) 

 remaining. The suspension is then plated out on Conradi- 

 Drigalski, malachite -green or brilliant -green, agar. This seems 

 to be a very promising method. 



4. Serum agglutination. A typhoid agglutinating serum, if 

 added to a medium containing typhoid bacilli, agglutinates the 

 bacilli, which aggregate into masses which may be centrifuged 

 out. But in any ordinary infected water the typhoid bacilli will 

 be too scanty to form masses, so Schepilewsky l adds 10 to 20 c.c. 

 of the water to flasks containing 50 c.c. of nutrient broth, which 

 are incubated at 37 C. for three to four days to induce multi- 

 plication of the typhoid bacilli, and then the typhoid serum is 

 added, and after standing for some hours and centrifuging, the 

 deposit is plated out. 



5. Process of Gambler. Cambier 2 devised a process based on 

 the idea that an actively motile organism will find its way through 

 the pores of a porcelain filter more quickly than feeble or non- 

 motile forms. His procedure is to make use of a special alkaline 

 peptone medium, which is placed-in a glass jar. In this is im- 

 mersed a Pasteur-Chamberland filter-candle half filled with the 

 same solution, to which is added a little of the fluid to be examined, 

 and the whole is incubated at 37 C. Sooner or later growth 

 appears in the fluid outside the candle, and Cambier states that 

 if typhoid bacilli be present they will make their appearance before 

 B. coli. In hands other than those of Cambier, however, the 

 method has not proved successful. 



6. Methods of inhibition. The principle of these methods is the 

 use of a medium which permits the growth of B. typhosus while 

 inhibiting the growth of B. coli and many saprophytes. In the 

 case of water, some means of concentration of the organisms must 

 first be employed (such as methods 1, 2 and 3 above), after which 

 the concentrated organisms are grown in the inhibiting medium. 



1 Centr. /. Bali., Orig., xxiii, No. 5, 1903. 



2 Rev. d'Hyg., 1902, p. 64. 



