6o 



Read as far as possible the chapters on this organism in 

 the text-books. Also article by T. Smith, The Am. Jour, of 

 Med. Sci., Sept., 1896, and by Adelaide W. Peckham, Jour- 

 nal of Kxp. Med., Vol. II., (1897) p. 549. 



97. General directions. Describe the appearance of 

 each of the cultures of B. coli communis made in Exercise 

 XXVIII. 



Bxamine the bacteria in a hanging drop preparation from 

 the bouillon and glucose bouillon cultures. 



Make and stain with carbol fuchsin a cover-glass prepara- 

 tion from the agar culture. Measure a few of the bacilli and 

 record their size in the notes. 



Note especially the quantity of gas formed in each of the 

 fermentation tubes. These cultures should be kept until the 

 next exercise when they should be examined again. If the 

 gas formation is then completed, determine the quantity of 

 gas and the ratio of the CO 2 to the H in the gas in each tube. 



Make two gelatin plates from the bouillon culture. In 

 making these plates use a tube of sterilized distilled water 

 for the first dilution. 



Test the culture in Dunham's solution for the presence of 

 indol. 



98. The indol test. Add i c.c. of a .01% solution 

 (fresh) of potassium nitrite and a few drops of concentrated 

 sulphuric acid to a culture in Dunham's solution or sugar free 

 bouillon. A pinkish color indicates the presence of indol. 

 It is sometimes necessary to wait several hours for a reaction. 

 In an old (3 to 5 day) culture the reaction is usually stronger 

 than in a more recently made one. 



