ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 339 



(4) Staining and Injecting. 



Staining the Hetina by Weig-ert's Method.* — Dr. R. Lennox hardens 

 the retina of man and of the cat in Muller's fluid and alcohol, and imbeds 

 in celloidin. The sections are jilaced for about twenty-four hours in a 1/2 

 to 1 per cent, chromic acid solution, and then, after having been washed in 

 water, in Weigert's hsematoxylin (1 part hfematox., 10 parts alcohol, 90 parts 

 water). If kept at a temperature of 40° C. they remained in the logwood 

 solution for two hours ; if at ordinary temperature, a longer time. The 

 sections were then decolorized by the cyanide solution (ferrocyanide of 

 potash 2-5, borax 2, water 100). When they became yellowish (about half 

 an hour) they were washed, dehydrated, and mounted in balsam. Nerve- 

 fibres (cat) came out as dark varicose threads. Two kinds of ganglion 

 cells were distinguished : — (1) large yellowish elements with bright nuclei 

 and black nucleoli ; (2) dark cells with perfectly black nuclei. In the 

 internal granular and epithelial layers (man) this difference of the nuclei 

 also occurs. The nuclei of the cones are usually black, those of the rods 

 bright with black nucleoli. Of these differences the author offers no 

 explanation. 



Staining^ Tubercle Bacillus.!— Herr Gottstein attacks Ehrlich's ex- 

 planation of the Ehrlich staining process, i. e. the investment theory which 

 supposes a qualitative difference, while Gottstein and others only accept 

 the presence of a quantitative difference. The author calls attention to the 

 fact that a property of certain constituents of the formula used for staining 

 renders it possible to dissolve twice as much of the dye as distilled water 

 would take up. Consequently the solution acts from concentration and not 

 by any specific virtue. Then as regards resistance to mineral acids, treat- 

 ment with decolorizing agents shows that the more lightly a dye is bound up 

 to the tissue the more easily is it disassociated therefrom, a confirmation of 

 Gierke's dictum that staining in general is not a chemical but a physical 

 process, and depends on diffusion and imbibition. The resistance of the 

 tubercle bacillus to decolorizing agents is to be explained, according to the 

 author, by supposing that it has a quantitatively slight disposition for 

 imbibition of solutions. 



Phenomenon in Anilin Staining.^ — Mr. E. H. Wagstaff in the summer 

 of 1884 mounted several slides of desmids, Spirogyra, and other algse, the 

 mounting substance being the article commonly known as " French polish," 

 coloured with the addition of a little anilin-green and well mixed to- 

 gether. The slides were spun in the usual manner on the turntable, the cells 

 being finally finished off with a last touching-up with the " French polish." 

 About six months after he found the specimens had become stained a 

 beautiful and vivid green, of course rather too vivid, but nevertheless quite 

 a surprise. The specimens stained were Spirogyra inflata, S. Weberii, S. 

 quinina, Stauraspermum gracile, and ;S^. viride. The desmids so treated 

 were Closterium rostratum in conjugation, and C. Leiblorii, &c. 



Congo Red.§ — Dr. F. Nissl gives the following (provisionally) as a 

 staining method for axis cylinders : — Chromate of potash ; alcohol, 95 per 

 cent. ; watery solution of Congo red, 5 to 400 ; alcohol, 95 per cent., three 



* Arch. f. Ophtlialm., xxxii. (1886) 8 pp. and 1 pi. 



t Deutsche Med. Wochenschr., 1886, No. 42. 



X Sci.-Gossip, 1887, p. 41. § Munchener Med. "Wochenschr., 1886, p. 528. 



