Differentiation of Tj^hoid and Colon Bacilli 609 



(0) Add I liter of water to 680 grams of finely chopped lean beef and place in 

 the cold for twenty-four hours. Expressthejuiceandmakeup to i liter. Coagu- 

 late the albumin, either by boiling for ten minutes or by heating to i2o°C. in 

 the autoclave. Filter. Add lo grams of Witte's peptone, 10 grams of nutrose, 

 and S grams of sodium chlorid. Heat in the autoclave at a temperature of 

 1 2o°C. for thirty minutes, or'boil vigorously for fifteen minutes. Render slightly 

 alkaline to litmus paper. Filter. Add 30 grams of agar. Heat in the autoclave 

 at a temperature of i2o°C. for one-half hour, or heat over the gas-flame until the 

 agar is dissolved. Render slightly alkaline to litmus paper while hot, if necessary. 

 Filter through glass wool into a sterile vessel. 



(h) To 130 cc. of litmus solution (Kubel and Tiemann's) add 15 grams of 

 chemically pure lactose. Boil for ten minutes. 



(c) Mix (ffl) and (6) while hot. Render slightly alkaline to litmus, if necessary. 

 To the mixture add 2 cc. of hot sterile solution of 10 per cent, sodium hydrate 

 in distilled water and 10 cc. of a fresh solution of Hochst's crystal violet (o.i 

 gram of crystal violet to 100 cc. of sterile water). 



The medium is now poured into Petri 

 dishes and is of a deep purple color. So 

 much water of condensation forms on the 

 solidified surface that it is an advantage to use 

 porous clay covers (Hill) for the Petri dishes 

 instead of the ordinary glass covers. The 

 medium keeps well but dries up rapidly. 



A very ingenious method of isolat- 

 ing the typhoid and colon bacilli from 

 drinking water has been suggested by 

 Starkey,* who uses a tubular laby- 

 rinth of glass filled with ordinary bouil- 

 lon containing 0.05 per cent, of car- 

 bolic acid, or, as recommended by 

 Somers,"]" Pariette's bouillon. The 

 original formula for the latter medium 

 is as follows: 



1. Measure out pure hydrochloric acid, 



4 cc, and add it to carbolic acid 

 solution (5 per cent.), loo cc. 

 Allow the solution to stand at least 

 a few days before use. 



2. This solution is added in quantities of o.i, 0.2, and 0.3 cc. (delivered by 



means of a sterile graduated pipette to tubes, each containing lo cc. 

 of previously sterilized nutrient bouillon). 



3. Incubate at 37°C. for forty-eight hours to eliminate contaminated tubes. 



The restraining medium prevents the ready growth of most organisms 

 except colon and typhoid bacilli. The anaerobic conditions prevent 

 the development of aerobic organisms which form the majority of 

 bacteria with which one comes in contact in ordinary bacteriological 

 examinations. The typhoid bacillus, being more motile than the 

 colon, travels more quickly through the coils of the labyrinth and first 

 arrives at its end, where it can be found in pure or nearly pure cul- 

 ture after about forty-eight hours. 



Somers has improved the labyrinth by bending it in a circular 



* "Amer. Jour. Med. Sci.," July, 1906, cxxxii, No. i. No. 412, p. 109. 

 t "Trans. Phila. Path. Soc," 1906. 

 39 



Fig. 253. — Starkey 's labyrinth as 

 modified by Somers. 



