FIXING AND HARDENING AGENTS. 53 



brain a mixture of 1 part methylated spirits with 3 parts of solution of 

 Miiller (see the chapter on the Central Nervous System in Part II ; see also 

 KULTSCHITZKY'S Mixture, ante, 59). Preparations should be kept in the 

 dark during the process of hardening in these mixtures. 



63. Cupric Sulphate. Not of general utility. See " Siphonophora." 



64. Alum. Alum has been used for fixing purposes. After an extended 

 experience of it, I only quote it in order to recommend that it be avoided at 

 all costs. 



65. Sulphurous Acid. WADDINGTON (Journ. Roy. Mic. Soc., 1883, 

 p. 185) uses a saturated solution of sulphurous acid in alcohol for fixing 

 infusoria. OVEETON (Zeit. f. iviss. Mik., vii, 1890, p. 9) uses an aqueous 

 solution for fixing algae. 



