Cleaning, Labeling, and Storing Slides 169 



of a cold soap solution, and then dried and polished. The slide must not 

 be left in the soap long enough to loosen the coverslip, or the coverslip is 

 likely to be removed when polishing the slide. 



Cleaning wholemounts made in resinous media is a rather different 

 procedure. It is necessary to wait until the resin has completely hardened, 

 hastened where necessary by exposure on a hot plate. Then as much of 

 the surplus as can be removed is scraped off with a dull knife. A small 

 lump of absorbent cotton saturated in 96 per cent alcohol is used to rub 

 off the remainder of the resin. It is not safe to try to clean a balsam slide 

 with benzene or xylene, for the coverslip will be loosened inevitably by 

 this method. As soon as the surplus resin has been dissolved away, the 

 slide is dipped immediately into a warm soap solution and then polished. 

 This leaves a very brilliant finish and an entirely clean slide. 



An additional reason why slides should always be washed in soap and 

 water after they are mounted is because there is no known method by 

 which a gummed paper label can be made to adhere to greasy glass. 

 More slides are rendered useless through the loss of their label than 

 from any other defect. Almost everyone today buys pregummed paper 

 labels, so that it is scarcely worthwhile in this text to give formulas for 

 label adhesives. There is, however, a very definite technique by which 

 the label may be made to stick most readily. This is to lick the upper sur- 

 face of the label, moisten thoroughly the lower surface, and then, when 

 both sides are fully expanded, to press it firmly on the glass. Labels 

 attached in this manner have remained for more than 20 years in the 

 author's collection without becoming detached. One may then either wait 

 until the label is dry before printing neatly on it with waterproof India 

 ink the name of the specimen or, if one is dealing with a large series of 

 slides, one may write the label first in waterproof India ink and, having 

 left it at least 24 hr to dry, attach it by the method indicated. 



Even if the label is attached by the method indicated, it is always best, 

 in the case of valuable slides, to write a brief label with a writing diamond 

 on the glass underneath the label. 



There is only one absolutely permanent method of labeling a micro- 

 scope slide, and that is to use a slide of which about an inch at the end 

 has been ground to a rough surface. After the slide is finished and cleaned, 

 the label is written on this ground surface either with a soft pencil or 

 with waterproof India ink. Then a drop of balsam is placed on the label 

 before attaching a coverslip over the the surface of it. The objections to 

 this method are that it is very expensive— the slides cost four or five times 

 as much as ordinary slides— and also that there is a grave risk that the 

 coverslip will be broken by someone placing the clip of the microscope 

 stage on top of it. 



The proper storage of microscope slides is just as necessary as proper 



