60 



Methyl green is one of the most delicate and precise of chro- 

 matin stains. It may be used alone or in combination, as in the 

 Ehrlich-Biondi mixture (111). A very dilute hematoxylin ( 88, 

 92) is excellent. 



176. Nucleoli. The Ehrlich-Biondi may be recommended 

 to bring out other nuclear structures, such as nucleoli, although 

 other combinations of basic and acid stains may be used. Mont- 

 gomery recommends Ehrlich's hematoxylin followed by a strong 

 aqueous eosin. 



177. Cytoplasm. Quite different pictures are obtained by 

 the use of fixers as similar in composition as Flemming's fluid and 

 Hermann's fluid, the difference seeming to be due to a varying 

 preservation of cytoplasmic "granules." The ground work of the 

 cell body, the so-called Spongioplasm, may be preserved by such 

 fixers as Zenker's fluid, Flemming's fluid, Hermann's fluid, Carnoy's 

 fluid, etc., and iron hematoxylin and the Ehrlich-Biondi mixture give 

 satisfactory stains. The granules that may be present are of different 

 kinds and often not easily interpreted; they include, (a) "re- 

 serve" material (yolk granules, fat granules, etc.), (b) basophile, 

 acidophile, neutrophile granules, (c) granules less easily preserved 

 which include many secretion granules, etc. 



(a) Yolk granules. If present in large amount a special fixer 

 may be indicated ( 20, 21, 22). 



Fat granules', see 224. 



(b) Basophile granulations (Granoplasma, Unna), may be 

 demonstrated by simple alcohol fixation and subsequent differential 

 staining with basic dyes. Compare 195 and the special technique 

 of blood ( 21 1-). 



(c) These require special technique: in general, (1) the employ- 

 ment of oxidizers such as dichromates, osmic acid, formalin, (2) 

 no acid, or a minimum amount. This seems to indicate the presence 

 of reducing substances usually lipoid in nature whose combinations are 

 soluble in (or rendered soluble by) acid. Here belong the Mitochon- 

 dria of Benda. 



178. Mitochondria. Benda's Method. 



1. Fix in Flemming's fluid with the acid reduced to 3 drops; 2. 

 Rinse in water, 1 hr.; 3. Place in equal parts pyroligneous acid and 

 1% aqueous solution of chromic acid, 24 hours; 4. 2% potassium 



