Cultivation 539 



a drop from this dilution is transferred to the second tube, and a drop 

 from it to a third, and then the contents of each tube are poured upon 

 a sterile plate, into a sterile Petri dish, or rolled, according to Esmarch's 

 suggestion, upon its own walls. The carbolic acid prevents the majority 

 of saprophytes from developing without inhibiting the typhoid bacillus 

 or, unfortunately, Bacillus coli communis. 



At the present time, with the development of the Widal 

 method of making a diagnosis by the agglutination of the 

 bacilli by the patient's blood, and the improvement of the 

 technic of the blood culture, the importance of recognizing 

 the typhoid bacillus in the feces has almost disappeared 

 as a diagnostic method. It is, however, of sanitary impor- 

 tance and, therefore, still claims attention. 



Fig. 167. Bacillus typhi abdominalis; superficial colony two days 

 old, as seen upon the surface of a gelatin plate. X 20 (Heim). 



Cultivation. Colonies. The deep colonies upon gela- 

 tin plates appear under the microscope of a brownish- 

 yellow color and spindle shape, and are sharply circumscribed. 

 When superficial, however, they become larger and form a 

 thin, bluish, iridescent layer with notched edges. The 

 superficial colonies are often described as resembling grape- 

 vine leaves in shape. The center of the superficial colonies 

 is the only portion which shows the yellowish-brown color. 

 The gelatin is not liquefied. 



Differentiation. Unfortunately, the appearances of the 

 colonies of the typhoid bacillus and the colon bacillus are so 

 similar as to make it impossible to recognize a single colony 



