APPENDIX. 385 



branes by preference) are brought fresh into a 4 per cent, solution of 

 methylen blue in physiological salt solution. After a few minutes therein 

 they are brought into saturated solution of picrate of ammonia, soaked 

 therein for half an hour or more, then washed in fresh picrate of ammonia 

 solution, and examined in dilute glycerin. 



If it be wished only to demonstrate the outlines of endothelium cells, the 

 bath in the stain should be a short one, not longer than ten minutes in 

 general. Whilst if it be desired to obtain an impregnation of ground-sub- 

 stance of tissue so as to have a negative image of juice-canals or other spaces, 

 the staining should be prolonged to fifteen or thirty minutes, and it is 

 advisable to remove the endothelial covering of the objects operated on 

 before putting them into the stain. 



If it be desired to preserve the preparations permanently, they had better 

 be mounted in glycerin saturated with picrate of ammonia. 



The effect is practically identical (except as regards the colour) with that 

 of a negative impregnation with silver nitrate. If the process bears out all 

 that is claimed for it, it will certainly be valuable ; for there are many 

 objects to which metallic impregnation cannot be readily applied. Marine 

 animals furnish many cases in point. 



767. Venice Turpentine for Mounting (VOSSELEE, Zeit. f. wiss. 

 Mik., vi, 3, 1889, p. 292, et seq.}. Vosseler strongly recommends this 

 medium as having considerable advantages over Canada balsam or damar. 

 Commercial Venice turpentine is mixed in a tall cylinder glass with an equal 

 volume of 96 per cent, alcohol, allowed to stand in a warm place for three 

 or four weeks, and decanted. It is stated that preparations may be mounted 

 in this medium without previous clearing with essential oils or the like. 

 The index of refraction being lower than that of the above-named balsams 

 delicate details are more distinctly brought out. Stains keep well in the 

 medium, and Vosseler states that he possesses preparations made fifteen 

 years ago that are perfectly well preserved. 



768. Gelatin-Soap Imbedding Mass (GODFEIN, Journ. de Bot., 1889, 

 5, p. 87 ; abstract in Zeit. f. wiss. Mik., vi, 3, 1889, p. 317). Very compli- 

 cated and, as far as I can judge from the report, rather of the nature of an 

 emulsion than of a homogeneous mass. 



769. Platino-Aceto-Osmic Mixture (HEBMANN, Arch. f. mik. Anat., 

 xxxiv, 3889, p. 58). The author obtained excellent results by substituting 

 1 per cent, platinum chloride for the chromic acid in Fleinniing's strong 

 formula, the other ingredients either remaining as before, or the osmium 

 being diminished one half. Thus 1 per cent, platinum chloride 15 parts, 

 glacial acetic acid 1 part, and 2 per cent, osmic acid either 4 parts or only 2 

 parts. Hermann found that protoplasmic structures are thus better pre- 

 served than with the chromic mixture, which appears to me very likely. 



770. Iodine Hsematoxylin (SANFELICE, Journ. de Microgr., xiii, 1889, 

 p. 335 ; Journ. Roy. Mic. Soc., 1889, p. 837). Dissolve 070 g. hsema- 

 toxylin in 20 g. absolute alcohol, and 0'20 g. alum in 60 c. c. distilled water. 

 Add the first solution, drop by drop, to the second. Expose the mixture to 



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