CHAPTER XXVI. 329 



blackening effect of the Os0 4 , one may then proceed to make 

 experiments. Several alternative methods may be tried : 



(a) The blackening may be extracted step by step in turpentine, and 



the appearance of the cell granules studied at intervals. 



(b) If the mitochondria are not stained black by the Os0 4 , one may 



proceed directly to Altmann's method (but preferably after 

 cautious treatment in -125 per cent, permanganate of potash). 



(c) The nuclear structures may be stained in safranin, crystal violet, 



or acid fuchsin. The sections are brought down to distilled 

 water and transferred to watery solutions of the dye. A few 

 minutes generally suffice to stain the nuclei. 



We find that in successful Mann-Kopsch preparations especially of 

 Invertebrata, the mitochondria do not generally become black, but are 

 either unstained or go yellowish. In many, but not all, cases it will be 

 found that where the mitochondria do become black after Os0 4 , the 

 colour is more readily extracted from them than from the Golgi elements, 

 BO that a distinction can nearly always be made by the Mann-Kopsch 

 method itself, without recourse to other methods which will generally 

 stain mitochondria and not Golgi apparatus (Regaud, Flemming, as 

 described in 679). Among the most useful differentiation or extraction 

 methods after Mann-Kopsch, turpentine is probably the best. The wax 

 is removed from the sections on the slide by means of xylol, and the 

 slide is transferred to a jar of turpentine. After about half a minute the 

 section is examined under a ^th-inch objective, and the effect of the tur- 

 pentine is noted ; one sometimes finds that the black colour in fat 

 globules and yolk spheres is extracted before a quarter of an hour has 

 elapsed, while the Golgi apparatus retains its black condition. In most 

 cases it is therefore possible to distinguish between yolk and fat on the 

 one hand, and the Golgi apparatus on the other. 



694. Mann-Kopsch-Altmann Combination (GATENBY, Journ. Roy. 

 Micr. Soc., 1921). If examination of the first Mann-Kopsch section 

 showed that the Golgi apparatus was blackened, and the mito- 

 chondria were either not stained or only straw or light-brown 

 coloured, one may proceed directly to the Altmann stain. Should 

 the examination show that the mitochondria as well as the Golgi 

 apparatus have become blackened, the sections must be extracted 

 in turpentine in an endeavour to remove the blackening from the 

 mitochondria. If the latter treatment does not succeed properly 

 the only course is to make new Mann-Kopsch preparations, -allowing 

 less time in the Os0 4 , say seven or eight days instead of the two 

 weeks. 



When one has succeeded in procuring sections in which the Golgi 

 apparatus alone is blackened, it is possible to stain in Altmann's 

 aniline acid fuclisin and picric acid method, so that the mitochon- 

 dria (and nucleoli) become red, the Golgi apparatus is black and 

 the ground cytoplasm yellowish. The Mann-Kopsch sections are 



