252 CEMENTS AND VARNISHES. 



CHAPTER XX. 



CEMENTS AND VARNISHES. 



430. Thanks to the efforts of the dilettanti to outshine one 

 another with neatly gaudy " rings," microscopical literature 

 contains a goodly show of receipts for cements and varnishes. 

 I have collected such as appear likely to be useful, rejecting 

 all that relates merely to ornament. 



Two, or at most three, of the media given below will 

 certainly be found sufficient for all useful purposes. For 

 many years I have used only one cement (Bell's). I recom- 

 mend this as a cement and varnish ; gold size may be found 

 useful for turning cells ; and Miller's caoutchouc cement may 

 be kept for occasions on which the utmost solidity is required. 



Marine glue is necessary for making glass cells. 



Carpenter lays great stress on the principle that the cements 

 or varnishes used for fluid mounts should always be such as 

 contain no mixture of solid particles ; he has always found 

 that those that do, although they might stand well for a few 

 weeks or months, yet always became porous after a greater 

 lapse of time, allowing the evaporation of the liquid and the 

 admission of air. All fluid mounts should be ringed with 

 glycerin jelly before applying a cement; by this means all 

 danger of running-in is done away with. 



The above passage stands as it stood, italicised as here, in the 1st and 2nd 

 editions. It was translated and amplified, in a special paragraph, in the 

 Traite des Meth. techniques. I may therefore be excused from hunting 

 up the name of the anatomist who recently published as new this old, old 

 method, or the pages of the journals which reproduced his paper without 

 protest. 



The reader who requires more information concerning 

 microscopical cements and varnishes than can be given in 

 this chapter may consult with advantage the papers of 

 AUBERT, The Microscope, xi, 1891, p. 150, and Journ. Roy. 



