636 SUMMARY OF CURRENT RESEARCHES RELATING TO 



quoted the triple staining method applied to fixed preparations of the 

 vascular bundles of Pteris aquilina. A section of such material shows 

 seven morphologically different tissues. First, it is treated with ethyl 

 violet [ethyl violet (0*25 p.c. in absolute alcohol; 5 c.cm. ; magnesium 

 sulphate 10 p.c, 15 c.cm. ; absolute alcohol, 20 c.cm. ; distilled water, 

 20 c.cm.] for several hours., washed in alcohol and reduced in 2 p.c. 

 watery sodium hydrosulphite. Then it is treated with 5 p.c. congo-red, 

 washed and reduced as before. Thirdly, Tan us green is applied, and 

 after the third reduction, tlie section is cleared, mounted, and examined. 

 The violet stain brings into evidence the scalarif orm and spiral tracheids. 

 The cell walls of the sieve tubes and of the pericycle, and the phloem 

 parenchyma are red, while the endodermis is green. The author illus- 

 trates his methods with excellent coloured plates. 



Individual Variation in Bacterial Staining.* — H. Kroneberger has 

 studied the results obtained by staining film preparations of certain 

 organisms with modifications of Gram's method. By using methylen- 

 blue or gentian-violet as the first staining solution ; using picric acid 

 solution either in place of or in succession to dram's iodine, and differ- 

 entiating with alcoholic eosin, four varieties of the classical staining 

 process are arrived at. If such organisms as staphylococci, streptococci, 

 and Bacillus coU are stained in these ways, it is found that individual 

 members of the same species are differentiated from one another. A 

 B. coU film for example may show red, light blue and dark blue bacilli. 

 The author regards sucli methods as individualizing stains, depending 

 upon biochemical variations in the bacilli investigated, and discusses in 

 general terms the nature of biochemical problems involved. Such 

 methods are of no diagnostic value. 



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



Paraffin Oil for Mounting Microscopical Preparations.! — G. 

 Giemsa finds that pure liquid paralfin may be used with advantage for 

 mounting preparations stained by the Romanowsky or the May-Grunwald 

 process. Such specimens when mounted in Canada balsam or cedar- 

 wood oil lose the greater part of their colour after a certain time. This 

 deterioration is more rapid and more marked in tropical climates. The 

 method of mounting in paraffin does not differ from that used for 

 Canada balsam. The coverglass should be fixed in position with a ring 

 of wax or gelatin, as the paraffin does not solidify. The author also 

 recommends the use of liquid paraffin for the purpose of storing unstained 

 film preparations until they are ready for examination. 



Use of Gelatin in Microscopical Technique.:]:— W. Johnson gives 

 the following description of a method for mounting microscopical speci- 

 mens in gelatin in place of Canada balsam. Sections may be prepared 

 by the freezing, paraffin, or celloidin methods. They can then be stained 



* Gentralbl. Bakt., Ite Abt. Orig., Ixxi. (1913) pp. 240-54. 

 t Gentralbl. Bakt., Ite Abt. Orig., Ixx. (1913) p. 444. 

 X Lancet, 1913, ii. p. 1062. 



