FUNDAMENTAL CONSIDERATIONS 27 



her on scale representing thickness in microns desired of sections and 

 turn wheel of microtome. It will be observed that the carrier moves 

 up and down and with each downward movement slightly forward, 

 causing the knife to cut sections which adhere in ribbons. 



Transfer the ribbons by means of a camel's hair pencil or dissecting 

 needle to a piece of dust free paper with the side downward which was 

 next to the knife. The ribbons are now ready to be mounted on 

 slides. 



The slides to be used should only be those which are devoid of 

 grease or dirt of any kind particularly on the surface upon which 

 the ribbons are to be mounted. A very good plan is to keep a number 

 of slides intended for this purpose submerged in a saturated solution 

 of potassium dichromate in concentrated sulphuric acid. These 

 can be taken out as needed and thoroughly rinsed with water. 



With a clean cloth stretched over the forefinger vigorously rub 

 one surface of each slide until perfectly dry and free of lint. Then 

 place a small drop of Mayer's albumin fixative on clean- surface and 

 rub over the surface. (The formula for Mayer's Albumin Fixative 

 is as follows: Egg white and Glycerin, equal parts, Carbolic acid 

 i or 2 drops. Mix thoroughly.) Now flood the surface with water 

 and cut the ribbons into segments of the desired length and arrange 

 in rows on slide, being careful to have the segments somewhat 

 shorter than the length of the cover slip because of tendency of 

 parafrine to stretch when warmed. Warm slide gently by holding 

 high above a bunsen flame or flame of an alcohol lamp until ribbons 

 stretch out in smooth fashion. Absorb superflous water from be- 

 neath ribbons with blotting paper held to their edges and at same 

 time push trie sections into even rows. Then leave the sections to 

 dry for several hours or over night. 



METHOD FOR THE STAINING AND MOUNTING OF MATERIAL IN 

 PARAFFINS RIBBONS AFFIXED TO SLIDE 



1. Gently heat the dry slides with parafrine ribbons adhering to 

 the fixative, high above the Bunsen flame (with the ribbon side up). 



2. Place the slide upright in. a well of xylol or turpentine. The 

 xylol or turpentine will dissolve the melted parafrine in a minute 

 or two. 



