INDUSTRIAL PROGRESS DURING THE YEAR 1874. c i 



of the softened gelatine in the centre of it ; now place the 

 confervae, or other object (previously dried as far as pos- 

 sible), on the gelatine, and gently warm over a lamp, simply 

 to melt the gelatine no more. . The object having been ar- 

 ranged, and the gelatine made to spread out as a thin sheet, 

 set the slide aside to cool. When cold, place a drop of bal- 

 sam thinned with benzole on the gelatine, warm the covering; 

 glass, place it over the object, squeezing out the superfluous 

 balsam, and set aside to dry. 



Mr. W. H. Jackson describes a new aniline staining fluid 

 which appears to have many advantages. He says: Prepare 

 a strong solution of tannic acid in water, dissolve a little 

 crystallized magenta in water in a test tube (or add Judson's 

 magenta to water). Both solutions must be cold. Add the 

 tannic acid drop by drop to the magenta, shaking the test 

 tube after adding each drop, and taking care not to pre- 

 cipitate the magenta entirely. Let the precipitate settle ; 

 pour off the fluid, and wash the precipitate by decantation 

 several times with cold water. Finally, let it partially dry, 

 and add just a drop of acetic acid, and then alcohol drop by 

 drop till it dissolves. The solution is pink. The following 

 preservative solutions, in mounting specimens stained by this 

 dye, are recommended. Both are made from sugar, and con- 

 sist of strong sirup, to which is added, to form solution A 

 (while hot), three to four per cent, of sodium chloride; and 

 to form solution B, the same quantity of calcium chloride: 

 the latter is practically uncrystallizable, whereas the for- 

 mer crystallizes with difficulty. If a section, after staining, 

 be immersed in cold water, it sets the dye, and the section 

 may be mounted in either of these fluids, and will remain 

 unchanged. 



Dr. Christopher Johnson recommends for blue and violet 

 stainings of vegetable tissues a dilution of the hamiatoxyline 

 staining fluid of Dr. J.W. S. Arnold, of New York, and also 

 an aqueous solution of aniline blue, made and labeled "blue 

 ink" by F. G. Bower & Co., New York. Arnold's fluid is pre- 

 pared by finely pulverizing logwood extract, and adding 

 about three times its bulk in powdered alum ; the two in- 

 gredients are well rubbed together with a small quantity of 

 distilled water: fifteen or twenty minutes' vigorous tritura- 

 tion will be necessary for a thorough incorporation ; water 



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