APPENDIX. 339; 



hydrate (serous glands). As a rule it is best to 

 te^se out the tissues in the fluid in which they 

 have been placed, they may also be teased in water 

 or in dilute glycerine ; if mounted in water they may 

 be temporarily preserved by heating the end of a 

 small wax taper in a flame, and with the wick smear- 

 ing the wax round the cover-slip. 



Hardening Agents. 

 General Directions. 



The tissues should be removed from the body to the 

 hardening agent as soon as possible after the death 

 of the animaL 



Any blood which may be on the piece of tissue should 

 be removed by shaking gently in salt solution or by 

 placing on blotting-paper. 



Divide the tissue (with a razor or sharp scalpel) into 

 small pieces before placing in the hardening fluid. 

 As a rule the pieces should not be more than 3 to 

 4 mm. square. Since the brain is too soft to allow 

 it. to be easily cut up without injury in the fresh 

 state, it is generally placed whole in the hardening 

 fluid, but in this way the deeper parts of the cortex 

 are in large brains rarely well preserved (cp. foot-note, 

 p. 327). 



In all cases where a tissue is put in a fluid to harden 

 or have lime-salts extracted from it, the fluid in 

 which it is placed should be relatively abundant, 

 e.g. 15 to 20 times the volume of the tissue; it 

 should be renewed after a time varying from 12 to 

 24 hours. 



