8o LABORATORY GUIDE IN BACTERIOLOGY 



REFERENCES 



Theobald Smith, The Wilder Quarter Century Book, 1893, 

 p. 187. 



Jordan, Journal o/ Hygiene, Vol. I (1901), p. 295. 



Durham, Journal oj Experimental Medicine, Vol. V, p. 353. 



1. Routine study. Observe carefully the growth on 

 potato of B. lactis aero genes. What is the cause of gas- 

 formation in this case ? 



2. Special study A. In order accurately to test the 

 action of micro-organisms on various carbohydrates, it 

 is necessary to eliminate the small amount of sugar in 

 ordinary broth introduced into it by meat-extract, which 

 generally contains muscle-sugar (glycogen). This is 

 accomplished by adding to freshly prepared broth a 

 culture of B. coli, which completely decomposes many 

 carbohydrates, including muscle-sugar. By this method 

 a sugar-free broth is prepared, which may be used as a 

 solvent for any sugar desired. 



Preparation of sugar-free broth for the fermentation- 

 tube: 



1 . Dissolve 



In water 400 c.c. 



Extract of beef i g. 



Peptone 4 g. 



by heat. Broth made from chopped beef (500 g. to i 

 liter) may also be used for this purpose. 



2. After cooling, inoculate with a broth-culture of 

 B. coli prepared 24 hours previously. 



3. Set aside in the locker, or, better, in the thermostat, 

 for 18-24 hours. 



4. Boil 5 minutes (to kill B. coli), and filter repeat- 

 edly through the same paper until perfectly clear. 



5. Divide into three equal parts and dissolve 2 g. 



