APPENDIX. 501 



be desired to submit to some other staining process or mount 

 in some other medium, may often with great advantage be 

 re- stained and re-mounted. All that is necessary is to put 

 the slide into a tube of xylol or benzol till the cover falls off 

 (about two days), wash well for some hours in clean xylol, 

 and pass through alcohol into the new stain. Since this was 

 pointed out to me by Dr. Henneguy I have unmounted and 

 re-stained a considerable number of old preparations, some 

 of them over fifteen years old, and have been most agree- 

 ably surprised at the results obtained. I have succeeded in 

 every case with series of sections mounted on Mayer's albu- 

 men, or by the water method. For shellac mounted series 

 E. MEYER (BioL Centralb., x, 1890, p. 509) removes the 

 covers and the balsam with chloroform, pours quickly a 

 2 per cent, solution of photoxylin or celloidin over the slide, 

 and after a few seconds brings it first into 70 per cent, 

 alcohol, then into 90 per cent., which dissolves the shellac, 

 then removes the membrane of collodion with the sections 

 under 70 per cent, alcohol, and stains. 



890. Gum for Labels. Labels stuck on glass often strip off. 

 This may be avoided (MARPMANN, Zeit. f. Angew. Mile., ii, 

 1896, p. 151 ; Journ. Roy. Mic. Soc., 1897, p. 84) by means 

 of the following adhesives : 120 grammes of gum arabic are 

 dissolved in a quarter of a litre of water, and 30 grammes of 

 gum tragacanth in a similar quantity. After a few hours 

 the tragacanth solution is shaken until it froths, and mixed 

 with the gum arabic solution. Strain through linen and add 

 150 grammes of glycerin previously mixed with 2 4 grammes 

 of oil of thyme. 



For other receipts see previous editions. 



891. Orientation (Addendum to 133, 134, 588). For 

 further details as to the BORN-PETER method of establishing 

 definition lines on paraffin blocks, see Verh. d. Anat. Ges., 

 xiii Vers., 1899 (Jena, Fischer), p. 134. 



892. Knife-heating Apparatus (Addendum to 135, p. 110) .- 

 An apparatus for warming or cooling both the knife and the 

 paraffin whilst cutting is described by HELD in Arch. Anat. 

 Phytt., Anat. Abth., 1897, p. 345. 



