ISOLATION OF BACILLUS TYPHOSUS 595 



centrifuged for fifteen minutes at 2000 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. An anti-typhoid serum the serum of 

 an animal which has been inoculated several times with the typhoid 

 bacillus, having the power of agglutinating typhoid bacilli if 

 added to a water would presumably agglutinate any typhoid bacilli 

 into masses which will sediment or may be centrifuged off. The 

 method has been used by Schepilewsky, 1 who adds 10 to 20 c.c. of 

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

 after three or four days incubation at 37 C. an addition of the 

 typhoid serum is made, and after standing for some hours and 

 centrifuging, the deposit is plated out. 



5. Method of enrichment. The principle of this method is to 

 devise a medium which will allow of the multiplication of the 

 typhoid bacillus and at the same time prevent, or at least retard, 

 the growth of B. coli and allied forms. Almost all the methods 

 which have been introduced for this purpose fail, inasmuch as 

 though they inhibit the growth of a great many organisms, they 

 do not inhibit the growth of the B. coli, or, if they do, inhibit the 

 B. typhosus to a still greater degree. Roth 2 found that caffeine 

 in broth would retard B. coli, but allow B. typhosus to multiply. 

 The method has been further elaborated by Hoffmann and Ticker, 3 

 who convert the water itself into a nutrient medium by the addition 

 of 1 per cent, of nutrose, 0-5 per cent, caffeine, and 0*001 per cent, 

 of krystal violet. The mixture is incubated at 37 C. for not more 

 than twelve to thirteen hours, at the end of which time the typhoid 

 bacilli should have multiplied to such an extent as to permit of 

 direct isolation by plating, the B. coli being inhibited. Many 

 observers have shown, however, that while caffeine may materially 

 help, it cannot be entirely relied on to eliminate B. coli and allied 

 forms. 



6. Process of Cambier. Cambier 4 has 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 feebly or non- 



1 Centr. f. Bakt., Orig., xxiii, No. 5, 1903. 



2 Hyg. Rundschau, xiii, 1903, p. 489. 



3 Ibid, xiv, 1904, p. 1. 



4 Rev. dHyg., 1902, p. 64. 



