134 ESSAYS ON BACTERIOLOGY. 



the public health and in view of the specific antitoxin 

 treatment. So true is this that in many cities, in- 

 cluding our own, laboratories and trained examiners 

 are provided, at 'public expense, for doing this and 

 similar work. Many progressive practitioners also in 

 smaller communities are becoming skillful in thus 

 making the diagnosis. The microscope alone, while 

 often affording a high degree of probability to the ex- 

 pert diagnostician, is not thoroughly reliable, since 

 other bacilli, similar in appearance to those of diph- 

 theria, may be found in the throat, or the specific mi- 

 crobes may to few and escape detection. Cultiva- 

 tions are therefore necessary, and, fortunately, are not 

 difficult. 



The bacilli of diphtheria stain fairly well with sim- 

 ple watery solutions of the basic anilin dyes. They 

 are most perfectly colored with the Lceffler alcoholic 

 solution of methyl blue containing a very small per 

 cent, of potassium hydrate. As thus stained, they 

 appear as straight or slightly curved rods, the ends 

 usually more strongly colored than the center, and 

 often staining in segments somewhat resembling a 

 chain of micrococci. A striking feature of these ba- 

 cilli is their variability of form, especially on different 

 cultiire media and in cultures or membranes of differ- 

 ent ages. 



Diphtheria bacilli grow most rapidly upon T.oeffler'a 

 ciilture medium, composed of three parts blood serum 

 and one part glucose-bouillon. In the incubator the 



