Staining Isolation 537 



and short; and in old gelatin cultures it forms long fila- 

 ments. 



Flagella. The organisms are actively motile and are 

 provided with numerous flagella, which arise from all parts 

 of the bacillus (peritricha), and are 10-20 in number. 

 They stain well by Loffler's method. The movements of 

 the short bacilli are oscillating ; those of the longer bacilli, 

 serpentine and undulating. 



Staining. The organism stains quite well by the ordinary 

 methods, but loses the color when stained by Gram's method. 

 The bacillus gives up its color in the presence of almost any 

 solvent, so that it is particularly difficult to stain in tissue. 



When sections of tissue containing the typhoid bacilli 

 are to be stained, the best method is to allow them to remain 

 in Loffler's alkaline methylene-blue for from fifteen minutes 

 to twenty-four hours, then wash in water, dehydrate rapidly 

 in alcohol, clear up in xylol, and mount in Canada balsam. 

 Ziehl's method also gives good results: The sections are 

 stained for fifteen minutes in a solution of distilled water 

 100, fuchsin i, and phenol 5. After staining they are 

 washed in distilled water containing i per cent, of acetic 

 acid, dehydrated in alcohol, cleared, and mounted. In such 

 preparations the bacilli are always found in scattered groups, 

 which are easily discovered, under a low power of the 

 microscope, as reddish specks, and readily resolved into 

 bacilli with the oil-immersion lens. 



In bacilli stained with the alkaline methylene-blue solu- 

 tion, dark-colored dots (Babes-Ernst or metachromatic 

 granules) may sometimes be observed near the ends of the 

 rods. 



The typhoid bacillus produces no endospores. 



Isolation. The bacillus is best secured in pure culture, 

 either from an enlarged lymphatic gland or from the splenic 

 pulp of a case of typhoid. To secure it in this way the 

 autopsy should be made as soon after death as possible, 

 lest the colon bacillus invade the tissues. 



No special precautions need be taken, as the bacilli are 

 usually present in pure culture. Care must be taken, how- 

 ever, to plant the culture in bouillon containing glucose, and 

 in milk in order that the absence of fermentation and 

 coagulation may make sure that no colon bacilli are pres- 

 ent. 



