210 CEMENTS AND VARNISHES. 



CHAPTER XX. 



CEMENTS AND VAENISHES. 



407. 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 Ziegler's white cement or zinc 

 white 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 edition. 

 It was translated and amplified, in a special paragraph, in the Traite des 

 Meth. Techniques. 1 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. 



408. Gelatin Cement (MARSH'S Section-cutting, 2nd ed., p. 

 104). Take half an ounce of Nelson's opaque gelatin, soak 

 well in water, melt in the usual way, stir in 3 drops of kreasote, 

 and put away in a small bottle. It is used warm. 



