BACTERIUM XEROSIS. 421 



minutes in the following solutions : Pyoktanin (Merck) 

 0.25 grammes, acid acetic (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 diphtheria? are stained bluish 

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

 organisms. The contour of the darkly violet stained 

 bacterium diphtherias 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 diph- 

 theria?? Wherein is the difference? 



In cultures and cover-slips made from both diph- 

 theritic and from innocent sore-throats are any organ- 

 isms almost constantly present? Which are they, and 

 what are their characteristics ? 



Which are the predominating organisms in the an- 

 ginas of scarlet fever? 



Do these organisms simulate, in their cultural and 

 morphological peculiarities, any of the different species 

 with which you have been working ? 



Do the diphtheria organisms disappear from the throat 

 with the disappearance of the membrane ? How long 

 do they persist? When obtained from the throats of 

 convalescents are they still pathogenic for guinea-pigs ? 



Prepare a bouillon culture of virulent bacillus diph- 

 theria? ; after it lias been growing for thirty-six hours 



