50 Botanical Microtechnique 



tares. The cutting ol ultra-thin sections is done sonietinies just to 

 show off one's skill tor publicit} purposes. However, every worker 

 gains some valuable experience by testing the potentialities ol avail- 

 able materials, equipment, and testing his skill by cutting some ultra- 

 thin sections. 



The very thin sections that are essential for electron microscopy 

 can be made with the attachment supplied by the American Optical 

 Co., Buffalo, N.Y., for their standard microtome, and with the sj^ecial 

 microtome made by the International Equipment Co., Boston, Mass. 



Affixing Paraffin Sections to the Slide 



Paraffin sections in the form of a ribbon are fastened to a glass 

 slide with an adhesive prior to staining. Adhesion is infhienced by 

 several factors, the most important being the following: 



1. Perfectly clean slides. 



2. An adhesive suitable for the particular material. 



3. Proper flattening of the sections by heat. 



4. Complete hardening of the adhesive, -which makes it insoluble in the 

 reagents used in staining. 



New slides shotdd be cleaned, although they may seem to be 

 clean. Use a soapless dish-washing detergent in 70'^ alcohol. Trade 

 names of the numerous suitable products will not be gi\en lure. New 

 products will undotdDtedly continue to appear on the market. The 

 present favorite in this laboratory is a concentrated licpiid detergent, 

 two droj)s of which in 200 cc. of 70% alcohol makes an effective 

 cleaner. Slides may be kept in a jar of this fitiid and wij)ed Avith a 

 clean lint-free cloth as needed. Cleaned slides de\eloj) a film on 

 standing, therefore it is best to clean them shortly before using. Used 

 slides can be cleaned with little effort and represent a considerable 

 saving. Slides that ha\e balsam or parallin on them shotdd be soaked 

 in lead-free gasoline for several hoin's, wiped dry and cleaned with 

 the detergent. Some workers use Bon .\mi for the Inial cleaning. 

 Examine used slides for excessive scratches and sinfacc corrosion. 

 Greasiness of the slide prc\ciits adhesion. Test the slides foi greasiness 

 as follows: piU two dro|)s of distilled water on the slide and spread 

 Aviili a scalpel. I'he water shotdd spread out thin on the glass. If the 

 edges of the water toll inward like \\ater on a hot plate, the slide 

 is greasy. 



The lornuilas oi the most connnon adhesivcs ((i\aii\c's) are 

 given in tlie references. The adhesive agent in most formulas is either 

 gum arabic, albinnen, or gelatin. Some modifications based on well- 



