222 SEEIAL SECTION MOUNTING. 



microscope slides will do for series of small sections.) Take 

 one of these plates ; lay the slip of paper with the sections 

 on the plate, the sections downwards ; press it down gently 

 and evenly, and the sections will adhere to the collodion, then 

 carefully remove the paper. (Do not place more than one or 

 at most two lines of sections on the same plate, for those first 

 placed run the risk of becoming dry whilst you are placing 

 the others.) This finishes the first stage of the collodionising 

 process. 



Now remove with blotting-paper any excess of alcohol that 

 may remain on or around the sections, pour collodion over 

 them, and get it to spread in an even layer. As soon as this 

 layer is dry at the surface you may write any necessary indi- 

 cations on it with a small brush charged with methylen blue 

 (the colour will remain fast throughout all subsequent manipu- 

 lations) . 



The plate may now either be put away till wanted in 80 per 

 cent, alcohol, or may be brought into a staining fluid. Wei- 

 gert recommends his haematoxylin process, but other watery 

 stains may be used. The watery fluid causes the double sheet 

 of collodion to become detached from the glass, holding the 

 sections fast between its folds. It is then easy to stain, wash, 

 dehydrate, and mount in the usual way, merely taking care 

 not to use alcohol of more than 90 to 96 per cent, for dehy- 

 dration. Weigert recommends for clearing the above- 

 described mixture of xylol and carbolic acid ( 305). Both 

 the dehydration and the clearing take rather longer with the 

 collodionised series than with free sections. 



The series should be cut into the desired lengths for 

 mounting whilst in the alcohol. It is perhaps safer to lay 

 them out for cutting on a strip of closet paper saturated with 

 alcohol. 



It is hardly necessary to comment on the great value of this 

 beautiful method. 



It is suggested by STEASSER that gummed paper might be an improvement 

 on the glass plates used in this process especially for very large sections. 

 See ante, 326. 



Other Methods. 



341. Giacomini's Collodion-Gelatin Method. See the chapter on 

 " Nerve-centres " in Part II. 



