Differentiation of Typhoid and Colon Bacilli 649 



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

 To the mixture a,dd 2 cc. of hot sterile solution of lo 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 dries up rapidly. 



A very ingenious method of isolating the typhoid and colon bacilli 

 from drinking water has been suggested by Starkey,* who uses a 

 tubular labyrinth of glass filled with ordinary bouillon containing 

 0.05 per cent, of carbolic acid, or, as recommended by Somers,t 

 Pariette's bouillon. The original for- 

 mula for the latter medium is as 

 follows : 



1. Measure out pure hydrochloric acid, 4 



cc, and add it to carbolic acid solu- 

 tion (5 per cent.), 100 cc. Allow the 

 solution to stand at least a few days 

 before use. 



2. This solution is added in quantities of 



0.1, 0.2, and 0.3 cc. (delivered by 

 means of a sterile graduated pipet to 

 tubes, each containing 10 cc. of pre- 

 viously 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 ex- 

 cept colon and typhoid bacilli. The 

 anaerobic conditions prevent the de- 

 velopment 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 culture after 

 about forty-eight hours. 



Somers has improved the labyrinth by bending it in a circular 

 form, so that it can stand alone, and by adapting its size to the Novy 

 jar, so that satisfactory anaerobic conditions can easily be attained. 



Hesse J has recommended the following medium: 



Fig. 260. — Starkey's labyrinth 

 as modified by Somers. 



Agar-agar. 



S grams (4.5 grams absolutely dry). 



Witte's peptone 10 



Liebig's beef-extract S 



Sodium chlorid 8.5 



Distilled water 1000 



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



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



i "Zeitschrift fur Hygiene," 1908, Lvm, 441. 



