ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 647 



which can be sloped as desired. Below the plane swept out by the knife 

 is the clamp for holding the preparation, and around it is a kind of 

 trough for receiving the liquid (water or alcohol) under which the 

 cutting is to be done. A micrometer screw bearing a notched disc 

 raises the preparation 0'005 mm. for each tooth. A balance weight over 

 a pulley takes the pressure oif the micrometer screw. 



Fig. 178 shows the earlier form in which trough and preparation 

 were both simultaneously moved ; fig. 179 a later form in which the 

 trough remained stationary and the preparation alone was raised. 



(4) Staining and Injecting-. 



Fungus and Bacterial Pigments.* — M. L. Matruchot advocates the 

 use of a pigment derived from Schizomycetes (Bacillus violaceus and 

 Bacterium violaceum), which he calls violacein. Experiments on its 

 reactions with the protoplasm of a fungus, Mortierella reticulata (see 

 p. 614), showed that it has selective properties, staining only the granular 

 protoplasm and leaving the hyaloplasm and the cell-membrane un- 

 coloured. Similar properties are possessed by the green pigment of 

 Fusarium polymorphum. This staining property must be distinguished 

 from " false pigmentation " (simple coloration by a foreign chromo- 

 genous organism) (Mucor, the Pyrenomycete of green wood), and from 

 " auto-pigmentation " (the coloration of an organism by the excretion 

 of its own pigment) (Monascus purpureus, Eurotiopsis Gayoni, E. 

 Saussinei, the Peziza of green wood, Mollisia Jungermanniae, Bacillus 

 erythrosporus). 



Kreso-fuchsin, a new Pigment.f — D. P. Kothig reports on a new 

 pigment, kreso-fuchsin, which appears to be a specific stain for elastic 

 tissue. Kreso-fuchsin is an amorphous powder, easily soluble in acetic 

 acid, sparingly soluble in alcohol, and very slightly in water. The 

 alcoholic solution has a blue, the aqueous a red colour. The alcoholic 

 solution stains elastic tissue dark blue, cartilage, keratin, and mucus red. 

 The aqueous solution does not stain elastic tissue at all, but cartilage, 

 &c. red. The formulae given by the author are two. The first or stock 

 solution is composed of kreso-fuchsin 0*5 grm., alcohol 75 per cent. 

 100 grm., hydrochloric acid 3*0 grm. The second or staining fluid con- 

 sists of stock solution 40 ccm., alcohol 95 per cent. 24 ccm., picric acid 

 1-2 ccm., aq. dest. 32 drops. 



The sections remain in the staining solution 2 hours or more ; an 

 immersion of 24 hours does no harm. They are then transferred to 

 95 per cent, alcohol, and afterwards to absolute alcohol in order to 

 remove excess of pigment and to dehydrate them. After passing through 

 xylol the sections are mounted in Canada balsam. In sections thus 

 prepared the elastic fibres are stained deep blue. Contrast and nuclear 

 stains may be used ; for these, orange G, carmin, borax alum, and 

 lithium carmin and hematoxylin are recommended. 



Neutral Red as a means for Diagnosing Bacterium Coli.J — Herr 

 W. Scheffler finds that B. coli commune produces a green fluorescence 



* Rev. Ge'n. de Bot. (Bonnier), xii. (1900) pp. 33-60. 



t Arch. f. Mikr. Anat. u. Entwickhm?s., lvi. (1900) pp. 354-61 (1 pi.). 



\ Centralbl. Bakt. u. Par., l te Abt., xxviii. (1900) pp. 199-205. 



