l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



and (luantity of material are considerations, or when a hard fixation 

 of perishable internal organ systems is desired for purposes of 

 dissection. If alcohol is used for preserving Coleoptera, strengths 

 neither exceeding 70 percent nor less than 50 percent are 

 recommended. 



XI. RELAXING 



The writer has found the relaxing mixture developed at the United 

 States National Museum by Herbert S. Barber to be extremely effi- 

 cient and versatile. In this fluid, ethyl acetate-killed specimens be- 

 come plastic almost instantly and genitalic dissections may be made 

 a very short time after immersion. It is invaluable for rejuvenating 

 old, greasy specimens, and will dissolve every mounting adhesive now 

 in common use. The formula is quoted below : 



Barber's fluid 



Ethyl alcohol (95 percent) 265 parts 



Water 245 parts 



Ethyl acetate (acetic ether) 95 parts 



Benzol (benzene) 35 parts 



Should the benzol separate out, a little alcohol, added slowly with 

 shaking, will serve to bring it back into the mixture. 



Relaxing alcohol-killed material preparatory to slip mounting pre- 

 sents a difficult problem. However, if such specimens are completely 

 dried under a lamp, then slightly moistened with Barber's fluid and 

 quickly blotted, recalcitrant appendages can usually be made to re- 

 main in the desired positions. A simpler and perhaps more efficient 

 method consists in a thorough soaking (several hours at least) in 

 chloroform. Articulations then become fairly easy to manage, espe- 

 cially in the smaller specimens whose appendages, while they are 

 still moist, readily yield to manipulation with needles. 



ACKNOWLEDGMENTS 



The author wishes to express his gratitude for the helpful sugges- 

 tions and encouragement received throughout the course of this 

 work from Edward A. Chapin, of the United States National 

 Museum, and from Herbert S. Barber and L. L, Buchanan, of the 

 Bureau of Entomolog)' and Plant Quarantine, United States Depart- 

 ment of Agrictdture. 



