127 



for temporsny inspection they may be laid in glycerine 

 after washing with distilled water ; but all except the 

 brown colors gradually fade in glycerine. Bismarck 

 brown is .for this reason, as well as for the cleanness of 

 its staining i.e., absence of granular precipitate per- 

 haps the most satisfactory for general use ; though in 

 special cases (tubercle bacilli and gonorrhoeal micrococci 

 for example) the blue and the red pigments are pre- 

 ferable. 



The violet (methyl and gentiana) dyes are especially 

 useful in the detection of amyloid degeneration ; for 

 while the normal elements are colored blue, those which 

 have undergone the amyloid change exhibit an intense 

 red color. This red tint rapidly disappears if the sec- 

 tions are placed in alcohol ; hence they cannot be 

 mounted in balsam, but may be kept (a certain time) in 

 glycerine. 



Bacteria which may be present in sections stained in 

 this way can be usually recognized at once (especially 

 when occurring in groups) by their intense color ; yet 

 their detection can be facilitated by taking advantage ot 

 the fact that these organisms not only absorb the aniline 

 colors readily, but retain these colors in the presence of 

 reagents which decolorize the other morphological ele- 

 ments that may be present : after exposure to such 

 agents, therefore, the bacteria are distinguishable at once 

 as the only intensely stained objects in the field. Occa- 

 sionally other objects than bacteria are encountered 

 which exhibit the same reaction the plasma-cells of 

 Ehrlich, nuclear detritus, globules of leucine. Ehrlich's 

 cells, moreover, simulate groups of micrococci some- 

 what closely, but can be usually distinguished by the 

 following characteristics : i, the granules of these cells 

 are rarely of uniform size, while the micrococci of a 

 zoogloea mass are ; 2, the granules composing the 

 cell usually surround a clear, oval space probably the 

 location of the nucleus ; no such appearance is pre- 

 sented by a group of micrococci ; 3, numerous plasma- 

 cells presenting a uniform appearance usually occur in 



