APPENDIX 277 



To use Endo medium: (a) make a lo per cent solution 

 of sodium sulphite in water; {b) make a lo per cent solution 

 of basic fuchsin in 96 per cent alcohol; (c) add 2 c.c. of 

 the fuchsin solution to 10 c.c. of the sulphite solution, pre- 

 pared as above, and steam a few minutes in an Arnold 

 sterilizer. 



7. Add I gm. of chemically pure lactose to each 100 c.c. 

 of Endo medium. 



8. Melt the Endo mediimi in streaming steam and add 

 ^ c.c. of the fuchsin-sulphite solution described above. 



9. Pom- plates, and allow them to harden thoroughly 

 in the incubator. 



The lactose used must be chemically pure, and the sul- 

 phite solution must be made up fresh every day. 



fflSS' MEDIA 



Two media are used: one for the isolation of the typhoid 

 bacillus by plate culture, and one for the differentiation 

 of the t>T)hoid bacillus from all other forms in pure cultiure 

 in tubes. 



Plate Medium. The plate medium is composed of 10 

 gm. of agar, 25 gm. of gelatin, 5 gm. of sodixun chloride, 

 5 gm. of Liebig's extract, 10 gm. of dextrose, and 1000 c.c. 

 of water. WTien the agar is thoroughly melted the gelatin 

 is added and completely dissolved by a few minutes' boiling. 

 The medium is then titrated, to determine its reaction, 

 phenolphthalein being used as an indicator. The requisite 

 amount of normal hydrochloric acid or of sodium hydrate 

 solution is added to bring it to the desired reaction; i.e., 

 + 2. To clear the medium add the whites of one or two 

 eggs, well beaten in 25 c.c. of water, boil for 45 minutes, 

 and filter through a thin filter of absorbent cotton. Add 

 the dextrose after clearing. The reaction of the medium 

 is most important; it should contain never less than 2 per 

 cent of normal acid. 



