STAINING ON THE SLIDE 207 



millimeter. As the ribbon comes off the microtome knife it is removed in 

 convenient lengths and laid in a series from left to right on a clean piece of 

 paper. The ribbons may be kept indefinitely imder a bell jar, but they are 

 best mounted as soon as convenient, since they will collect some dust no 

 matter what precautions are taken. 



The ribbons are made to adhere to the slide with a fixative of the follow- 

 ing formula (Mayer's albumen fixative) : 



white of egg 50 cc. 



glycerin 50 cc. 



sodium salicylate 1 gram 

 Mix well and filter. The sodium salicylate is an antiseptic and the fixative 

 will keep for several months. Place a very small drop on the slide and with 

 the tip of the little finger spread the thinilest film that can be laid on evenly 

 over it. Then cover the film of fixative with water and place the ribbons 

 cut to the proper lengths upon the water, arranged as desired. Warm the 

 water gently over a flame; the paraffin will soften and the ribbons will 

 expand and become perfectly smooth. The paraffin should not be allowed 

 to melt. Drain the water ofi carefully and arrange the ribbons, which will 

 now lie in a film of water, over the fixative. Put the slide aside to dry. It 

 is frequently convenient to warm the ribbons in the water by placing the 

 slide on the top of the paraffin bath and then to dry the slide in the same 

 way, protected from too much heat by several thicknesses of blotting paper. 

 The preparations are not ready for staining on the slide until perfectly 

 dry. They may be kept thus indefinitely, but it is best to stain soon, 

 since the surface of the ribbons will inevitably collect dust. A great saving 

 of time can be secured by preparing a number of slides at a time and carry- 

 ing them simultaneously through the above processes and those of staining 

 on the slide. 



STAINING ON THE SLIDE 



197. Preparation for staining on the slide. The dry slides with the ribbons 

 adhering to the fixative may be placed in the bath to melt the paraffin, or 

 they may be gently heated over a flame (with the ribbon side up), a process 

 which must be managed carefully so as not to scorch the sections. The 

 slide is then placed upright in a well of xylol (Stender dishes are convenient), 

 which should not be near the flame. The xylol will dissolve the melted 

 paraffin in a minute or so. The slide is then taken out of the well (the under 

 side wiped off) and either placed in a well of 95% alcohol or a stream of 

 alcohol is run over it from a pipette or wash bottle. The slide is now ready 

 to be placed in the staining wells, of which there are various forms, but 

 Stender dishes are satisfactory. 



