ZOOLOGY AND BOTANY/, MICROSCOPY, ETC. 371 



mixture. That number of drops of ammonia (probably between 4 and 

 8) whicb decolorises the metbylen-blue in from £ to 1 minute is taken 

 as the standard, and the necessary quantity calculated on this basis is 

 added to the remainder of the sterile H 2 S water in the measuring 

 cylinder. After thoroughly mixing, this NH 4 HS solution is added to 

 each of the tubes of nutrient media iu the proportion of 1 : 10. 



Isolation of the Typhoid Bacillus.* — Dr. A. Moore recommends a 

 modified Eisner agar medium for isolating the typhoid bacillus. 500 

 grm. of potato are scraped on a grater, and then macerated in a litre of 

 water for 3 or 4 hours, strained and allowed to stand overnight. Next 

 morning the supernatant fluid is decanted off and the volume made up to 

 1000 ccm. The liquid is then rendered distinctly alkaline and 20 grm. 

 of agar added. The process is then continued as for ordinary agar. 

 When sterile the medium is distributed into test-tubes, 10 ccm. in each, 

 and immediately before use 0*5 of the following solution is added to 

 each tube: — Potassium iodide 10 grm., water 50 ccm. The agar tubes 

 thus contain 1 p.c. of potassium iodide. Plates made with this medium 

 were sown with mixed cultures of the typhoid and coli bacilli and incu- 

 bated for 24 hours at 37°. After this interval examination under a low 

 power showed that the typhoid colonies were clear, transparent, with 

 irregular clean-cut margins, while the coli colonies were larger, rounded, 

 and opaque. By this procedure typhoid bacilli were isolated in pure 

 culture from numerous artificial mixtures, from old typhoid dejecta, and 

 from cockles suspected of causing an outbreak of typhoid fever. 



The author also describes experiments with W-shaped tubes contain- 

 ing Parietti's serum-gelatin. Though successful for isolating any given 

 strain of colon bacillus the method failed when applied to mixtures of 

 different strains, and though possessing a certain value, was abandoned 

 for the method given above. 



Medium for Isolating 1 Typhoid Bacilli, f — V. Drigalski and H. 

 Conradi have constructed the following medium for isolating typhoid 

 bacilli. (1) 3 lb. of beef are macerated in two litres of water for 24 

 hours. The beef extract is then boiled for an hour, and after having 

 been filtered, 20 grm. pepton, 20 grm. nutrose, and 10 grm. salt are added. 

 The mixture is then boiled for an hour, and after filtration 20 grm. of 

 the best agar are added. After boiling for 3 hours the solution is 

 rendered alkaline, filtered, and boiled for h hour. 



(2) 260 ccm. of litmus solution (Kubel-Tiemann) are boiled for 10 

 minutes, and then 30 grm. of chemically pure lactic acid are added. This 

 mixture is boiled for 15 minutes. 



(3) The two foregoing solutions, while still quite hot, are mixed 

 together, and having been well shaken, 4 ccm. of a hot sterile solution of 

 10 per. cent, crystalline soda and 20 ccm. of a freshly prepared solution 

 of 0-1 grm. crystal violet B. Hochst, in 100 ccm. of warm distilled 

 water, are added. Plates are then made in the usual way. 



The authors claim that a diagnosis of typhoid can be made by means 

 of this medium always within 24 hours, the typhoid colonies being blue 

 and quite transparent while the coli colonies are red and opaque. 



* Brit. Med. Journ., 1902, i. pp. 703-4 (1 fig.). 



t Zeitachr. Hyg. u. Iufekt., sxxix. (1902) pp. 283-300 (1 flg.)- 



