n8 



BACTERIOLOGICAL LABORATORY TECHNIC 



the reaction of the medium and each batch should be tested, then 

 marked whether faintly or strongly acid or alkaline. 



Thrust absorbent cotton to the bottom of the tube and wet 

 with distilled water; place the potato upon the 

 cotton, then plug the tube and sterilize in auto- 

 clave twice. The tubes should be sealed. 



PEPTONE SOLUTION Dunham 



Take Peptone 10 grams. 



Salt 5 grams. 



Water 1,000 c.c. 



Mix. Boil. Filter and store in tubes and sterilize. 



This is used to demonstrate the production of 

 indol. Reaction should be neutral. 



SUGAR MEDIA 



One of the most important parts of determinative 

 bacteriology is the discovery of the different fer- 

 mentative powers upon carbohydrates of otherwise 

 similar germs. Monosaccharides (dextrose and 

 galactose), disaccharides (lactose, saccharose), 

 alcohols (glycerine mannite) and some starches 

 (dextrin, inulin) are in common use daily in the 

 laboratory to show the enzyme action of various 

 species, indicated by acidity and gas production. 

 One percent solutions of these carbohydrates are made in neutral 

 broth or agar. The best method is to prepare a 20 percent 

 solution of the material, sterilize it in the steam sterilizer and add 

 from this to the stock medium sufficient to make the required 

 percentage. This avoids repeated heating. The media should 

 be neutral. Addition of litmus tincture or Andrade's indicator 

 (100 c.c. of .5 percent watery acid fuchsin decolorized by the 

 addition of 16 c.c. N/i NOOH) will supply an index for acid 

 production. 



FIG. 27. Po- 

 tato in culture 

 tube. (Wil- 

 liams.) 



