94 Special Senses. 



acid have been added. Kemove when the bone is 

 softened. 



When the bone is decalcified by either of these pro- 

 cesses, it must be washed for several days, to remove 

 the lime salt. It is then ready for cutting sections. 

 In the case of the internal ear, sections are much better 

 cut by hand, as the fine structures such as the rods of 

 Corti are quite disarranged by freezing, and cutting 

 with a microtome. 



The bone must now be placed in gum solution, for 

 24 hours, and then removed to spirit slightly diluted 

 with water. If the spirit is too strong, the gum will 

 form a substance like chalk, and quite as hard ; this 

 can, however, be softened by placing it in water. When 

 the gum is sufficiently hardened by the spirit, it can be 

 embedded in wax mass, and sections cut by hand in the 

 ordinary manner. These sections must be very gently 

 handled, and should not be lifted with a needle but with 

 a fine camel hair pencil. They are best stained in log- 

 wood. It is a good plan to stain the whole bone in 

 logwood before placing it in the gum solution, but care 

 must be taken that it is not too deeply stained. The 

 undiluted logwood should be used, and it will require 

 about 6 hours or more to stain it thoroughly. 



Sections must be cut through the semi-circular canals 

 and also through the cochlea, and the cochlea should 

 be so embedded that sections will be cut through its 

 whole length. 



