390 PREPARATIONS BY THE COLLODION METHOD [Ch. XI 



to harden the cementing collodion. After 15 minutes, or longer if 

 convenient, put the mounted specimen into the clamp of the micro- 

 tome and cut as above. 



Sometimes when the imbedded object is of sufficient size and the 

 collodion block is firm, the block itself is put into the microtome 

 clamp, no wood or cork holder being used. 



§ 633. Transferring sections from the knife to the slide. — When 

 one has cut the number of sections for one slide, they should be trans- 

 ferred to the slide as follows: Take a piece of white tissue paper 

 about 3X6 centimeters in size and lay it on the knife over the sec- 

 tions. Press down slightly so the paper is in contact with all the 

 sections. Take hold of the paper beyond the edge of the knife and 

 gradually pull it down off the knife. 



If there is the right amount of alcohol on the knife, the sections 

 adhere to the paper and move with it. This transfers the sections 

 from the knife to a piece of tissue paper. Place the tissue paper with 

 the sections down on the middle of an albumenized slide. Cover 

 with another piece of paper and press down gently. This presses the 

 sections against the slide and absorbs a part of the alcohol. Take 

 hold of one edge of the paper and lift it with a rolling motion from the 

 slide. The sections should stay on the slide (§ 633a). 



§ 633a. — Various forms of paper have been used to handle the collodion 

 sections. It should be moderately strong, fine-meshed, not liable to shed 

 lint, and fairly absorbent. One of the first and most successful papers recom- 

 mended is " closet or toilet paper." Cigarette paper is also excellent. In my 

 own work the heavy white tissue paper has been found almost perfect for the 

 purpose. Ordinary lens paper or thin blotting paper for absorbing the alcohol 

 or oil may be used with it. 



§ 634. Fastening the sections to the slide. — With a pipette, drop 

 95 % alcohol on the slide of sections, then use a pipette full of abso- 

 lute alcohol if it is at hand. Drain most of the alcohol away and 

 add a few drops of ether alcohol. The collodion should melt and 

 settle down closely on the slide. If the collodion does not melt the 

 dehydration was not sufficient and more alcohol must be used. After 

 the collodion has melted down upon the slide let the slide remain a 

 minute or two in the air, and then transfer the slide to a jar of 67 % 

 alcohol (fig. 232). 



