646 Typhoid Fever 



of the colon, paracolon, typhoid, and paratyphoid baciUi, the typhoid 

 baciUi alone exhibiting the specific effect of the t5^hoid serum. This 

 is a very rehable means of diifferentiation when the cultures have 

 already been isolated. The method is described under the heading 

 "Agglutination," in the section devoted to the "Special Phenomena 

 of Infection and Immunity." 



Richardson* has found it very convenient to saturate filter-paper with typhoid 

 serum, dry it, cut into 0.5 cm. squares, and keep it on hand in the laboratory for 

 the purpose of making this differentiation. To make a test, one of these little 

 squares is dropped in 0.5 cc. of a twenty-four-hour-old bouillon culture of the 

 suspected bacillus and allowed to stand for five minutes. A drop of the fluid 

 placed upon a slide and covered will then show tjrpical agglutinations if the 

 culture be one of the typhoid fever bacillus. In a second mention of this methodf 

 he has found its use satisfactory in practice and the paper serviceable after four- 

 teen months' keeping. 



The Cultural Diferentiation. — ^When the t5^hoid bacilli are to be 

 isolated from the blood of living patients, they are so likely to be 

 obtained in pure culture that little trouble is experienced. If they 

 are to be isolated from the pus of a posttyphoidal abscess, or from 

 viscera at autopsy, from water suspected of pollution, and especially 

 when they are to be isolated from the intestinal contents, with its 

 rich bacterial flora, the matter becomes progressively complicated. 



As the colonies of the typhoid bacilli closely resemble those of 

 Bacillus coli, etc., special media have, from time to time, been 

 devised for the purpose of emphasizing such differences as rapidity of 

 growth, acid production, etc., Eisner { suggested the employment 

 of a special potato medium, and Remy§ an artificial medium ap- 

 proximating a potato in composition, but without dextrine or glu- 

 cose. These media have ceased to be used. 



Wiirtz|| and Kashida** make the differential diagnosis by observ- 

 ing the acid production of Bacillus coH in a medium consisting of 

 bouillon containing 1.5 per cent, of agar, 2 per cent, of milk-sugar, 

 I per cent, of urea, and 30 pea: cent, of tincture of litmus. This is 

 the so-called litmus-lactose-agar-agar . The culture-medium should 

 be blue. When liquefied, inoculated with the colon bacillus, poured 

 into Petri dishes, and stood for from sixteen to eighteen hours in the 

 incubator, the blue color passes off and the culture-medium becomes 

 red. If a glass rod dipped in hydrochloric acid be held over the dish, 

 vapor of ammonium chlorid is given off. The typhoid bacillus pro- 

 duces no acid in this medium, and there is consequently no change in 

 its color. Upon plates with colonies of both bacilli, the t3^hoid 

 colonies produce no change of color, while the colon colonies at once 

 redden the surrounding' medium. 



* "Centralbl. f. Bakt. u. Parasitenk.," 1897, p. 445. 

 t "Journal of Experimental Medicine," May, 1898, p. 353, note. 

 i "Zeitschrift fiir Hygiene," 1895, xxii, Heft i; Dec. 6, 1896. 

 § "Ann. de rinst. Pasteur," Aug., 1900. 

 I] "Archiv. de med. Experimentale," 1892, iv, p. 85. 

 ** "Centralbl. f. Bakt. u. Parasitenk," June 24, 1897, Bd. xxi, Nos. 20 and 21. 



