408 



BACTERIOLOGY. 



half to two minutes in the following solutions : Pyok- 

 tanin (Merck) 0.25 grammes, 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 diphtherias 

 are stained bluish black, are large, and may be seen in 

 almost all of the organisms. The contour of the darkly 

 stained bacterium diphtherias is sharply denned, and it 

 is very easily differentiated from any other organisms 

 that may be present in the preparation. 



FIG. 70. 



Bacterium diphtheria?, stained by Neisser's method. 



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- 

 therise? Wherein is the difference? 



In cultures and cover-slips made from both diph- 



