374 MANUAL OF BACTERIOLOGY. 



and the great motility of the typhoid bacillus produces a uniform clouding 

 of the medium in tubes, without gas-formation, characters which distinguish this 

 organism from the colon bacillus; in plate -cultures with this medium the colonies 

 exhibit peculiar filamentous outgrowths. It is claimed that it can be determined 

 whether organisms are typhoid bacilli or not after thirty-six hours in the incu- 

 bator by this method. 



Other special media for the identification of the typhoid bacillus have been 

 devised by Eisner, Stoddart, by Capaldi and Proskauer, and by Piorkowski.* 

 The medium of Stoddart is based upon principles similar to those applied in 

 the medium of Hiss. 



The Drigalsky-Conradif method for isolating the B. typhosus from water 

 and feces is that now most employed. The principle of this method consists 

 in the use of a culture-medium on which the surface colonies of B. coli and of 

 B. typhosus each show a characteristic, macroscopic appearance, so that they 

 can be separated from one another. Furthermore, the medium employed is 

 unfavorable to the growth of many bacteria likely to be present. 



The addition of crystal violet to the milk-sugar-litmus-agar inhibits the growth 

 of various organisms without materially affecting the growth of B. typhosus. 

 The medium adopted by Drigalsky and Conradi after many trials was as 

 follows : 



(a) Three pounds of chopped beef placed over night in 2 liters of water. 

 Strain off, and boil for one hour, filter and add 20 grams of Witte's peptone, 

 20 grams of nutrose, and 10 grams of salt. Boil one hour, filter and add to it 

 60 grams of best stick agar; boil three hours over the flame or one hour in the 

 autoclave, make slightly alkaline to litmus paper, and boil one-half hour. 



(6) 260 c.c. litmus solution (Kubel and Tiemann); boil for ten minutes; 

 add 30 grams of c. p. milk-sugar, and boil the mixture fifteen minutes. 



(c) Add solution b to the hot, melted solution a; mix thoroughly and correct 

 the reaction to weakly alkaline if not already so. 



(d) Add 4 c.c. of a hot, sterile 10 per cent, solution of dehydrated soda. 



(e) Add 20 c.c. freshly prepared T ^ per cent, solution of crystal violet (Kry- 

 stallviolet "B," Hochst). This solution should be made with warm, sterilized, 

 distilled water, but not boiled. 



A part of this agar is poured into Petri dishes at once. The rest is kept in 

 flasks, about 200 c.c. in each. 



The material to be examined is spread over the surface of the plates, not 

 mixed with the medium as is usually done, the object being to obtain surface 

 colonies only. 



The spreading is done by means of a glass rod 12 or 14 cm. long, bent at right 

 angles about 3 cm. from one end. The short arm of the bend terminates 

 in a small knob, and is dipped into the material to be examined and run over 

 the surface of the agar in a series of the previously prepared Petri dishes. 



Drigalsky-Conradi plates, as described above, are made from water by using 

 the precipitate after centrifuging. 



Ficker and Hoffmann! recommend the following method of treating the 



*Elsner. Zeitschrift fur Hygiene. Bd. XXI., p. 25. 1895. Stoddart. 

 Journal of Pathology and Bacteriology. Vol. IV., p. 429. 1897. Capaldi and 

 Proskauer. Zeitschrift fur Hygiene, etc. Bd. XXIII., p. 452. 1896. Pior- 

 kowski. Berliner klinische Wochenschrift. p. 145. 1899. 



fDrigalsky-Conradi. Ueber ein Verfahren zum Nachweis der Typhus- 

 bacillen. Zeitschrift fur Hygiene und Infectionskrankheiten. Bd. XXXIX. 

 1902. 



| Ficker and Hoffmann. Weiteres iiber den Nachweis von Typhusbacillen. 

 Archiv fur Hygiene. Bd. XLIX. 1904. 



