348 SPECIFIC MICRO-ORGANISMS 



colonies while the colon and aerogenes bacilli will have produced 

 larger colonies colored pink to deep red or even showing a metallic 

 , luster of the f uchsin. In every test it is wise to inoculate one plate 

 with a fecal suspension to which a known culture of the organism 

 in question has been added so that there may be known standard 

 colonies for comparison. The suspected colonies are then, trans- 

 planted to Russell's double-siigar medium, an agar^ containing 

 I per cent lactose, o.i per cent glucose and Andrade's indicator. 

 This medium is slanted so that the lower end of the tube is entirely 

 filled with agar for a depth of one half inch with the inclined sur- 

 face above this. Each colony is transplanted by stabbing the 

 inoculating needle deep into the cylindrical butt of the tube and 

 also stroking the inclined surface, the result being a combined 

 streak and stab-culture. After incubation for 24 hours any of 

 these cultures which show a growth characteristic of the typhoid 

 bacillus, that is, pink butt and almost colorless upper portion 

 under the streak, without any gas bubbles, are tested for aggluti- 

 nation against a known an ti- typhoid agglutinating serum. The 

 examination is thus completed in two or three days. 



The specific antibody ordinarly sought in the blood is the 

 typhoid agglutinin. A few drops of blood in a Wright's capsule 

 sufl&ce for the microscopic test (see page 218). A young active 

 culture (broth three hours) of a known B. typhosus is used, and 

 the serum is tested in dilutions of 1:20, i :4o and i :8o, observed 

 for an hour. Normal serum rarely shows any clumping in any of 

 these dilutions at the end of an hour. Th's agglutination test is 

 of little or no value if the patient has received typhoid vaccine 

 within a year. 



Dreyer^ and his coworkers have devised a technicfor measuring 



' The double-sugar medium is a 2 to 3 per cent agar, neutral to litmus, to which 

 has been added i per cent lactose and o.i per cent glucose. On this medium B. 

 typhosus does not change the color when it is growing on the surface, but produces 

 a red (acid) color about the stab. See Russell, Journ. Med. Rsch., 1911, Vol. XX, 

 pp. 217-229. 



''Dreyer and Inman, Lancet, July 31, igrs, p. 225; Dreyer and Torrens, ibid., 

 191S, ii, p. 1369; Dreyer, Walker and Gibson, ibid., Feb. 13, 1915, p. 324; Dreyer and 



