BACTERIUM XEROSIS 475 



cases to regard all bacteria that do not stain in the way 

 described as distinct from bacterium diphtherise. 



Blumenthal and Lipskerow^ decide that the differential 

 method which yields the most satisfactory results consists 

 in the fixation of the preparation for from one-half to two 

 minutes in the following solutions: Pyoktanin (Merck) 

 0.25 grams, acetic acid (5 per cent.) 100 c.c; washing in 

 water and counterstaining with a 1 to 1000 solution of 

 vesuvin for one-half minute. By this method the polar 

 granules of bacterium diphtherise are stained bluish black, 

 are large, and may be seen in almost all of the organisms. 

 The contour of the darkly stained bacterium diphtherise 

 is sharply defined, and it is very easily differentiated from 

 any other organisms that may be present in the preparation. 



Note. — Prepare cover-slip preparations from the mouth- 

 cavities of healthy individuals and from those having decayed 

 teeth. Do they correspond in any way with those made 

 from diphtheria? Do the same with different forms of 

 sore-throat. Do the peculiarities of any of the organisms 

 suggest those of bacterium diphtherise? Wherein is the 

 difference? 



In cultures and cover-slips made from both diphtheritic 

 and from innocent sore-throats are any organisms almost 

 constantly present? Which are they, and what are their 

 characteristics? 



Which are the predominating organisms in the anginas 

 of scarlet fever? 



Do these organisms simulate, in their cultural and mor- 

 phological peculiarities, any of the different species with 

 which you have been working? 



1 Centralblatt f. Baoteriologie, Bd. xxxviii, p. 359. 



