DEHYDRATION 63 



is certain that alcohol has a hardening effect, which is, up to a 

 point, of very considerable importance. Thus, while a frog 

 embryo can be dehydrated in less than two hours in the various 

 strengths, the end result is not so good as when the process is 

 lengthened to a day or to forty-eight hours. This hardening 

 effect, in the case of some objects, like insects, is inimical to the 

 best results, and some workers use other varieties of alcohols 

 (§ 127) especially for the higher strengths which harden most. 

 Thus it may be necessary when using ethyl alcohol, to shorten 

 periods in the 90 and 100 per cent, strengths as much as possible 

 consistent with proper dehydration. In § 1240, are some notes on 

 dehydrating plant material. 



125. Other Methods of Dehydrating. In the following para- 

 graphs are given a few of the more recently tried methods. It 

 should be noted that for general purposes none of these techniques 

 has the general advantages of ethyl alcohol and xylol or carbon 

 bisulphide, in cheapness and reliability ; but for entomological and 

 botanical work, such methods as the amyl alcohol, methylal and 

 dioxan, will have a restricted usefulness. They may be regarded 

 as quite unsuitable for routine work in students' laboratories. 



126. Amyl alcohol has been a good deal used since it was 

 suggested by Hollande (C. R. Soc. de Biol., 1918). It is recom- 

 mended by Hartridge {Journ. Physiol., 1920). This alcohol does 

 not mix with water, but is miscible with 90 per cent, ethyl alcohol, 

 toluol and xylol. Beyond the fact that it is less hydroscopic than 

 ethyl alcohol, it is difficult to see its advantages in routine work. 

 The fact that it does not mix with water is a serious objection to 

 it. It does, however, dissolve paraffin wax, and it is possible to go 

 straight from this alcohol into amyl paraffin mixtures, which in 

 the case of some material, may be very important. 



127. N- Butyl alcohol * has been utilised for insects ; its use in 

 microtomy was joroposed by Mile. Larbaud (C. R. Acad. Sc, 

 1921). It has been especially studied by Karl A. Stiles {Stain 

 Tech., 1934), H. M. Smith {Turtox News, 9, 1931) and L. ]VL\r- 

 GOLENA (Stain Tech., 1932). Stiles mentions that he got very 

 good results with insect material. He used Gilson fixed insects 

 which were transferred to 35 per cent, ethyl alcohol for thirty 

 minutes to one hour, then to a mixture of 9 c.e. of 45 per cent, 

 ethyl alcohol + 1 c.e. of butyl alcohol for two hours, then 8 

 c.c. of 62 per cent, ethyl alcohol -f- 2 c.e. of butyl alcohol for two 

 hours, then 65 c.c. of 77 per cent, ethyl alcohol + 35 c.c. of butyl 

 for four hours, then 45 c.c. of 90 per cent, ethyl + 55 c.c. of 

 butyl for six hours to days, then 25 c.c. of 90 per cent, ethyl + 

 75 c.c. butyl for six hours to overnight with one change, finally 

 butyl alcohol alone, two changes at intervals of several hours. 

 Pieces may be stored apparently indefinitely in butyl alcohol. 



* See also § 1257. 



