FIXING AND PRESERVATIVE MEDIUMS 33 



Good results depend entirely upon complete insensibility 

 before killing, and this is tested by touching the tentacles, or 

 branchial appendages, with a needle (Lo Bianco, pp. 450 and 

 468). 



Such Radiolarians as Aulacanthidcs and the Acanthometrce 

 are, says Lo Bianco (p. 444), plunged directly into alcohol of 

 50 per cent, and after some hours into that of 70 per cent. 



Such oceanic Hydrozoa as Physophora, Agalma, and 

 Halistemma are hardened immediately in alcohol of 35 per 

 cent., and after two hours are placed in alcohol of 70 per cent. 

 (Lo Bianco, p. 45 5). 



The common " starfishes " are prepared, says Lo Bianco 

 (p. 458), with their ambulacral feet extended, by causing them 

 to die in alcohol of 20 to 30 per cent., arranging them in the 

 vessel with their ambulacral area uppermost. 



One-third Alcohol. — This, says Mr. Lee, is useful for fixing, 

 but care should be taken that 90 per cent alcohol only is used, 

 and objects may not be left longer than twenty-four hours in 

 this mixture, or maceration takes place ; its chief use, therefore, 

 is for extemporaneous and dissociation preparations. It is 

 known as Ranvier's alcohol, " alcohol au tiers," " Drittelalcohol," 

 or " Ranviersche Alcohol dilutus," and " alcool al terzo." 



Alcohol and Glycerin. — Mixtures of these fluids have been 

 used for many purposes, and Mr. Lee considers them valuable 

 for delicate objects, especially when it is necessary to bring 

 them from weak into strong glycerin ; he regards the following 

 as one of the best, and preferable to alcohol in which to retain 

 objects already fixed, until required for dissection or other 

 purposes. 



4. — Calberla's Liquid 



Alcohol , . ) 



Glycerin . ,■ Equal parts 



Water . ) 



