ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 521 



in thick cedar oil. Blood films may also be stained by the following 

 method : — 1 c.cm. of the stock solution is diluted with 20 c.cm. of 

 distilled water, and the film which has been previously fixed in absolute 

 alcohol immersed therein for 20-30 minutes, after which it is washed in 

 water, dried and mounted in cedar oil. Rapid staining of Treponema 

 pallidum may be effected by means of this stain in the following 

 manner : 10 c.cm. of 5 p.c. glycerin are mixed with 10-12 drops of the 

 stock solution. This mixture is boiled for a few seconds and poured 

 hot over the preparation previously fixed in absolute alcohol. After 



3 minutes the film is washed in water, dried and mounted in thick 

 cedar oil. 



Staining the Mycelium of the Dry-rot Fungus.* — W. Ruhland 

 fixes the material for a few minutes in • 8 p.c. chromic acid, to which 

 1 p.c. acetic acid is added, and then washes for 2-3 hours. The ob- 

 jects are then mordanted 6-24 hours in 1*5 p.c. iron-alurn solution, 

 and then heated with a formal hematoxylin solution of the following 

 composition : 1 grm. hematoxylin crystals, 200 c.cm. distilled water, 



4 c.cm. formalin. The solution is shaken and filtered. The mycelium 

 flakes may remain herein for 12-24 hours, though less may suffice. After 

 washing again, they are differentiated in 0*5 p.c. iron-alum solution. 

 This takes a few minutes to half an hour. Then washing in water, 

 alcohol, xylol, balsam. The plasma is bluish; the nuclei, bluish-black to 

 black. 



Theory of the Gram Staining Method.f — Y. Brudny made an 

 elaborate investigation as to the why and wherefore of the Gram staining 

 reaction. He finds that it is clue to the specific permeability of Gram- 

 positive bacteria to iodine. This expresses in other terms that for 

 certain bacteria the lugol solution acts as a mordant, and that the 

 alcohol decolorises or not, though it must be admitted that there are 

 intermediate stages in the reaction. 



(5) Mounting-, including- Slides, Preservative Fluids, etc. 



Technique of the Water Method of Sticking Paraffin Sections 

 on the Slide. J — J. F. Gudernatsch washes the slide with some good 

 potash soap under the tap, and then picks up the section, which has 

 been floated on the surface of water in a bowl. After arranging the 

 section, the superfluous water is poured off ; the slide, covered with 

 something to protect from dust, is placed in an incubator until all the 

 water has evaporated. In this way the sections are not only flattened 

 out, but are stuck on, and it only remains to dissolve out the paraffin in 

 the usual way, and then pass the sections through the ordinary staining 

 and other fluids. If there be any need for hurry, the sections, when 

 arranged on the slide, may, instead of being placed in the incubator, 

 be mopped up, and at the same time flattened out by means of 

 blotting-paper. Then, after a stay of about 3 minutes in the incubator, 

 the sections will be found to have adhered. This procedure, however, 

 is frequently not so successful as the one previously described. 



* Arb. biol. Anstalt. f. Land. u. Forstw., v. (1907) p. 492. 

 t Centralbl. Bakt., 2te Abt , xxi. (1908) pp. 62-79. 

 j Zeitscbr. wiss. Mikrosk., xxiv. (1908) pp. 357-60. 



