Notes on Microtechnique 323 



NOTES ON MICROTECHNIQUE 11. 



M. S. Markle, Earlham College. 



The damage done to recently mounted microscopic slides by a class 

 of freshmen is well known; yet is it often impossible to anticipate one's 

 needs sufficiently to allow time for slides to harden. This is especially 

 true of slides mounted in Venetian turpentine, which hardens more slowly 

 than balsam. I have found that slides may be used at once, after being 

 mounted according to the following method. 



The Venetian turpentine into which the material is finally brought 

 is allowed to dry until it is quite hard — so thick that its surface may 

 be indented with difficulty. This is softened by being placed on a 

 warming-plate. The material when sufficiently warmed to be thin enough 

 for ready mounting is placed on the slide on another hot-plate, the 

 material is arranged with needles, a cover is added and the material 

 allowed to fill the space under the cover. 



With a little more care, stem sections, and even paraffin sections 

 may be mounted in balsam in the same manner. I have been much 

 surprised to find what extreme temperatures sections will endure with- 

 out damage. By accident, some slides of Marchantia antheridia were 

 mounted and left on a hot-plate 22 hours. I supposed they would be 

 ruined, but careful examination showed no damage. A thermometer 

 placed on the hot-plate showed a temperature of 145° C. 



A convenient hot-plate for such work or for stretching paraffin rib- 

 bons or for warming inibedding-dishes while the pieces of material are 

 being arranged may be made by mounting an ordinary electric bulb 

 inside a box over which a piece of glass has been placed. A discarded 

 photographic negative is satisfactoiy. For higher temperatures, a piece 

 of zinc or sheet brass is better. Temperatures may be modified by 

 varying the wattage of the electric bulb used. Very high temperatures 

 may be gotten by mounting the bulb vertically and placing over it a 

 tin cylinder covered with asbestos paper. A thin lantern slide plate 

 was used for several weeks over the hot-plate mentioned above as giving 

 a temperature of 145° C. without breakage. 



I have been using with gi^eat satisfaction the gelutin-glycerin fixa- 

 tive described in the Botanical Gazette, April, 1919, by Artschwager. I 

 use phenol instead of sodium salicylate. The results are superior to 

 those obtained by the use of egg albumen. 



Even with the best of fixatives, some materials persist in coming 

 off the slide during the staining-process, especially when aqueous stains, 

 such as the haematoxylins, are used. Following a suggestion by Dr. 

 F. D. Lambert, of Tufts College, I have used with excellent results the 

 following method. After the paraffin has been dissolved in xylol and 

 the xylol has been removed with alcohol, the slides are dipped in a very 

 weak solution of celloidin in alcohol and ether. The slides are removed, 

 allowed to drain but not to dry and are carried through the staining- 

 process in the usual way. Celloidin stains heavily in haematoxylin, but 

 ! y the time the destaining is completed, no trace of the stain remains in 



"Pioc. :!8th Meeting. lf)22 (192;!)." 



