256 PATHOGENIC BACTERIA. 



The organism stains quite well by the ordinary meth- 

 ods, but loses the color entirely when stained by Gram's 

 method. Its peculiarity of staining is the readiness with 

 which the bacillus gives up its color in the presence of 

 solvents, so that it is particularly difficult to stain it in 

 tissue. 



When sections are to be stained the best method is to 

 allow the tissue 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 fif- 

 teen minutes in a solution of distilled water 100, fuch- 

 sin 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 may be found in little groups, 

 which are easily discovered, under a low power of 

 the microscope, as bluish specks, and readily resolved 

 into bacilli with the high power of the oil-immersion 

 lens. 



In bacilli stained by this alkaline methylene-blue solu- 

 tion dark-colored dots may sometimes be observed near 

 the ends of the rods. These dots were at first regarded 

 as spores, but are now denominated polar granules, and 

 are thought to be of no importance. 



The typhoid bacillus is both saprophytic and parasitic. 

 It finds abundant conditions in nature for its growth and 

 development, and, enjoying strong resisting powers, can 

 accommodate itself to environment much better than the 

 majority of pathogenic bacteria, and can be found in 

 water, air, soiled clothing, dust, sewage, milk, etc. con- 

 taminated directly or indirectly by the intestinal dis- 

 charges of diseased persons. 



The bacillus is also occasionally present upon green 

 vegetables sprinkled with water containing it, and an 

 epidemic is reported in which the infection was traced to 

 oysters from a certain place where the water was infected 



