64 DEHYDRATION 



Imbedding is done by transferring to a mixture of 2 parts 

 paraffin wax to 1 of butyl alcohol (melting-point 56° to 58° C.) in a 

 covered Stender dish in the oven for twelve to twenty-four hours, 

 which is afterwards uncovered until the odour of the butyl alcohol 

 disappears, after which the pieces are transferred to pure 

 paraffin wax. Long periods of infiltration are absolutely 

 necessary, and do not harden either plant, vertebrate, or insect 

 tissues as might be expected. 



In defence of this complicated and tedious technique, it may be 

 stated that such insects as aphids cut very nicely, and the end 

 result is probably better than with diaphanol. The times given 

 above are not rigid, insects may be left longer periods in the grades 

 without hurt. It may be noted that only 8-3 grm. of /«-butyl 

 alcohol are soluble in 100 c.c. of water. The dehydrating power of 

 this alcohol is therefore low. 



128. Iso- and normal propyl-alcohols are excellent substitutes 

 for absolute ethyl alcohol and mix in all proportions with water, 

 xylol and cedar oil (W. C. Clothier, Watson's Microscope Record, 

 No. 31, 1934.) 



129. Ethylene Glycol Mono-Ethyl Ether (Cellosolve) has been 

 suggested as a dehydrating agent by H. F. Frost {Watson's 

 Microscope Record, No. 34, 1935). It is expensive, inflammable 

 and rapidly absorbs water from the air. We do not know whether 

 it has any physiological action when breathed in small quantities, 



130. Dioxan (Di-ethylene oxide, M.P. 11°, B.P. 101°) has come 

 into use in many laboratories. This liquid is a remarkable solvent. 

 It mixes with water, alcohol, xylol and dissolves balsam and 

 paraffin wax. It is a dangerous substance, and has a marked 

 physiological and cumulative action. It is unsuitable for students' 

 laboratories, and should only be used for special work. Its 

 advantages are not so considerable that they outweigh the fact 

 that it will have an effect on the health of laboratory workers. It 

 has been said that it will preserve intra-vital stains in fixed pre- 

 parations, and enable stained bodies to be studied in permanent 

 preparations. With neutral red we have not found this to be so, 

 but it is true that very good preparations may be prepared from 

 materials dehydrated and imbedded in dioxan and dioxan wax 

 mixtures. Introduced in 1931 by Graupner and Weissberger 

 {Zool. Anz., Bd. 96) into microtomy, it is much used in chemistry 

 also as a solvent. It is a useful substance for making celluloid 

 cements. Since it has little odour, it is possible to breathe toxic 

 proportions in air, without knowing that one is doing so. It will 

 be particularly dangerous in those small, improperly ventilated 

 rooms so often used for imbedding and section cutting. 



With this warning we give the method. From many fixatives 

 it is possible to go straight into dioxan, which is changed three 

 times, and then pass to dioxan and wax — finally pure wax ; thus 



