BACILLUS TYPHOSUS 497 



and the alteration in the color of the colon colonies appears 

 too early. For this reason it is also necessary to liquefy 

 the agar as quickly as possible in pouring plates from the 

 agar medium stored in flasks. 



In employing this culture medium it is necessary to have 

 a uniform suspension of a portion of the material to be 

 examined and to make a series of plate inoculations from 

 this suspension by smearing carefully the material under 

 consideration over the surface of the medium in the plates, a 

 sterile platinum spatula or a sterile bent glass rod being used 

 for the purpose. 



After fourteen to sixteen hours at 37° C, and still better 

 after twenty to twenty-four hours, the cultures are readily 

 differentiated: 



a. Bacillus Coli: All cultures of true colon that have been 

 examined form colonies of 2 to 6 or more millimeters in 

 diameter, of reddish color and translucent. In each intes- 

 tinal evacuation there are usually several varieties of 

 colon colonies which differ according to their size and tex- 

 •ture, translucency, and the intensity of the alteration of 

 the color which they bring about. Many colon colonies 

 are bright red, some are cloudy, and others are quite opaque, 

 dark-wine red in color, while still others form large colonies 

 which are surrounded by a red halo. 



b. Bacillus Typhosus: The colonies have a diameter of 

 1 to 3 millimeters, rarely larger. Their color is blue, with 

 a tendency toward violet. In structure they are glistening, 

 with a single contour, somewhat of the nature of a dew drop. 

 Only in isolated instances is the colony larger and more 

 cloudy in appearance. 



The Endo Media. — (Modification of Kendall and Day.) 

 Prepare the following: 

 32 



