602 SUMMARY OF CURRENT RESEARCHES RELATING TO 



in 70 p.c. alcohol) for one to three hours, and then, after slight washing 

 in 70 p.c. alcohol, in a 0*5 p.c. solution of pure brazilin in 70 p.c. spirit. 

 Three to sixteen hours are required to give a good sharp definition. 

 After staining, the sections are washed in pure 70 p.c. spirit, passed 

 through the usual stages, and mounted. Over iron-haematoxylin this 

 method possesses two advantages : the sections are never taken down 

 into water, and the number of washings is considerably reduced. The 

 results are satisfactory, for not only is brazilin a definite chromatin stain, 

 but in nearly all tissues some parts of the cytoplasm are also stained, 

 though of a different colour, and with some tissues it is a triple stain. 



Methylen-Azur and the Red Reaction of Methylen-Blue. * — Dr. 

 L. Michaelis points out that the metachromatism of alkaline methylen- 

 blue solutions is due to the presence of the decomposition product 

 methylen-azur, called by Nocht " the red from methylen-blue," while 

 methylen-red is an impurity introduced in or unremoved by manufacture. 

 He has devised the following method of making an azur-methylenblue. 

 2 grm. of medicinal methylen-blue are dissolved in 200 ccm. of water, 

 and to the solution 10 ccm. ^L normal soda solution are added. The 

 solution is then heated and kept boiling for ^ hour. The fluid is allowed 

 to stand till it cools, when 10 ccm. -^ normal sulphuric acid are added, 

 after which it is filtered. 



For staining purposes one part of the solution is mixed with 5 parts 

 1 per thousand eosin solution and the mixture well shaken. The pre- 

 parations are left in the solution for J hour, after which they are washed 

 in water, dried, and mounted. Differentiation in alcohol or in eosin 

 solution is unnecessary. 



Microscopic Injections with Cold Fluid Gelatin.f — Dr. J. Tandler 

 prepares a stained injection mass which remains fluid in the following 

 way : — 5 grm. of finely divided pure gelatin are soaked in 100 grm. 

 of distilled water and afterwards heated. When the gelatin is melted, 

 Berlin-blue is added, and then 5-6 grm. of potassium iodide are gradu- 

 ally worked in. As a rule the mass will keep fluid and injectable down 

 to 17° C, but should it set, the addition of more iodide will prevent the 

 recurrence. Some crystals of thymol should be added, and the mass 

 preserved in stoppered bottles. The animals should be injected im- 

 mediately after death, and then the pieces to be preserved are immersed 

 in 5 p.c. formol. This fixative is very advantageous for staining and 

 decalcification afterwards, as the chemical changes which take place ai - e 

 very slight. 



(5) Mounting - , including- Slides, Preservative Fluids, &c. 



New Formula for Preserving' Zoological and Anatomical Speci- 

 mens.J — G. Marpmann finds that by adopting the following formula the 

 alcohol may be omitted from his method. The preparations are first 

 immersed in the following mixture : — sodium fluoride 50 ; formaldehyde 

 (40 p.c.) 20 ; water 1 litre. From this fixative solution they are trans- 

 ferred to the preservative fluid, composed of glycerin 28° B 5 litres ; 



* Centralbl. Bakt., l' e Abt, xxix. (1901) pp. 763-9. 



t Zeitschr. wiss. Mikr., xviii. (1901) pp. 22-4 (1 pi.). 



J Zeitschr. angew. Mikr., vii. (1901) p. 14. Cf. this Journal, 1899. p. 456. 



