Chromosomes 369 



Colchicine pretreatment is efficacious, suppressing cell division, 

 preventing spindle formation and allowing the chromosomes to 

 spread. They shorten and thicken and become straight and can be 

 fixed into almost a single plane when squashed. Use 0.01-0.02% 

 aqueous solution of colchicine for 2-3 hours, and follow by fixation, 

 etc. {Burrell, 1939; O'Mara, 1939; Meyer, 19-13) 



Permanent Mounts 



If a slide is to be made into a permanent mount and there is a chance of 

 losing the specimens, coat the slide with albumen before smearing. 



A. Smith {1947) method: 



1. Remove paraffin or vaseline seal with razor blade and xylene. 



2. Soak in equal parts of acetic acid and 95% alcohol until cover 

 glass comes off^. 



3. Place in equal parts of 95%, ethyl alcohol and tertiary butyl 

 alcohol: 2 mintUes. 



4. Transfer to tertiary butyl alcohol, 1-2 changes: 2 minutes each. 



5. Briefly drain slide and cover glass against absorbent paper or 

 blotter. 



6. Add thin resin mountant to slide and return cover glass to same 

 position as before. 



Step 2 can be followed by 2 changes of 95% ethyl alcohol; mount 

 in Euparal or Diaphane. 



B. Xolts {194S) method: 



1. Place slide in covered dish so edge of cover glass dips into 95% 

 alcohol: 6-12 hotirs. 



2. Immerse in 95% alcohol: 1-2 hotns. 



3. With sharp needle, gently pry cover glass free ^vhile immersed. 



4. Drain off excess alcohol and add drop of Euparal or Diaphane 

 and replace cover glass. 



C. Other permanent methods: 



McClintock {1929); Celarier {1956); and Bradley {1948B). Peary 



{1955) uses a frozen method of dehydration, also counterstains Avith 



fast green. 



Delamater {1951) describes a freezing method. 



Conger and Fairchild {1953) freeze smears while in stain on a block 



of dry ice: 30 seconds. Pry off cover glass with razor blade. Place 



before thawing in 95% or absolute alcohol, 2 changes: 5 minutes. 



Motmt in Etiparal or Diaphane. 



