The Glycerin Method 93 



3 to 24 hours in a J per cent aqueous solution of haematoxylin. 

 Wash again in water for 20 minutes, and then place the material for a 

 second time in the iron solution. The material must now be exam- 

 ined every few minutes, since the iron solution extracts the stain. 

 When the stain is just right, wash in water for 1 to 4 hours. If the 

 iron solution is not washed out thoroughly, its continued action will 

 cause the preparations to fade. 



Put the material into 10 per cent glycerin (1 part glycerin and 9 

 parts water), and then allow the water to evaporate gradually in a 

 place as free from dust as possible. Minots, or watch crystals, are 

 good dishes for this purpose. The white glass covers of " Hazel' 

 jars could hardly be surpassed. Petri dishes are also good, but rather 

 expensive. When the glycerin has become about as thick as pure 

 glycerin, the material is ready for mounting. A little to the right of 

 the center of the slide, place a drop of glycerin in which the material is 

 lying. In the drop place a little of the material, taking care not to use 

 more than can be spread out without making a confusing tangle. Use 

 scissors constantly so as not to injure filaments by trying to pull them 

 out from a tangle. There should be just enough glycerin to come to 

 the edge of the cover-glass, but not any more, for it is impossible to 

 seal a mount if glvcerin has oozed out bevond the cover. 



o \j *j 



The mount should now be sealed. Canada balsam, various 

 asphalts, cements, and glues have been used, but the best and 

 cheapest of all seems to be the ordinary flat varnish, or gold size, 

 used by painters in laying gold leaf. Choose a gold size of about the 

 color of the varnish used for ordinary woodwork. Mounts which 

 had been sealed with gold size more than fifty years before have 

 been exhibited in perfect condition, but they must have been hidden 

 away in some museum, for a glycerin mount would never survive 

 fifty years of laboratory use. The gold size, as painters use it, is 

 likely to be too thin for sealing mounts. Put some of it in a one- 

 ounce bottle with a wide neck and leave the cork out until the gold 

 size thickens a little. Should it become too thick, thin it with 

 turpentine. 



Nothing but practice will enable one to spin a good ring, but 

 a good camePs-hair brush, a good turntable, and a gold size neither 



