7.S0 SUMMARY OF CURRENT RESEARCHES RELATING TO 



immersed in the ammoniacal silver nitrate solution at 87-40° in the 

 dark for 24 hours. On removal they are washed in 1 p.c. ammonia for 

 10 to 15 minutes, followed by distilled water and staining as before. 



Though the results are the same in all three procedures, the author 

 recommends fixing in Carnoy's fluid, and treating the pieces in toto with 

 the ammoniacal silver reagent. The purin bodies are seen in the cells 

 or within the tubules as black granules, which vary much in size. 



H ansen, ;F. C. C. — Ueber die Ursachen der metacb.romatiscb.en Farbung bei 



gewissen basischen Farbstoffen. 



Zeitschr. loiss. Mikrosh., xxv. (1908) pp. 145-53. 



„ „ Ueber Eisenhamatein, Chromalumhamatein, Tonerdealaun- 



hamatein, Hamateinlosungen und einige Cochenillefar- 

 bldsungen. Op. cit., xxii. (1905) pp. 45-90. 



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



Farrants' Medium.* — Farrants' medium, says H. S. Ogilvie, is very 

 apt to give trouble by the formation of air-bells in the mounts. These 

 often originate in the making of the medium, through stirring it too 

 vigorously. Before use, filter it through a fine linen or spun glass-cloth, 

 previously washed in distilled water. This process takes some time, 

 therefore protection from dust and undue evaporation should be provided. 

 The secret in mounting with this medium is to use a very liberal supply ; 

 it is also advantageous to use a rod for transferring it instead of a 

 pipette. The specimen, having previously lain two or three days in some 

 of the mountant, is placed on a slide, carefully arranged, and then a 

 comparatively large quantity of the medium is placed upon it. Air- 

 bells may then be removed either to the edge with needles, or by bursting 

 them with a hot needle. Apply the cover-glass very gently, and do not 

 press it down for two or three days, and even at the end of that period 

 do so very gradually. After a week or two the excess of medium may 

 be cleaned away, and the slide allowed to dry. If the edges refuse to 

 dry, use less glycerin in the preparation of the mixture. The same 

 remarks apply to Dean's medium, and glycerin-jelly ; excepting that, in 

 the case of the last-mentioned, the cover-glass should be pressed home at 

 once, the superfluous jelly cleaned away when cold, and the slide ringed. 

 The advantages derived from any of the foregoing are chiefly : 1 . Their 

 low refractive index, which renders delicate unstained tissue more easily 

 seen than would be the case were balsam used. 2. By their use, previous 

 •dehydration, which sometimes causes contraction, is avoided. In either 

 of these respects one medium is practically as good as the other. 3. In 

 many cases such media are as useful as a liquid, with the advantages 

 that they are easier to use, and the risk of subsequent leakage is avoided. 

 In the preparation of any of these mixtures, be careful to avoid glycerin 

 that has been diluted with water. 



* English Mechanic, lxxxviii. (1908) p. 240. 



