THE PREPARATION OP ANIMAL TISSUES. 43 



to be washed free from all trace of the acids, and 

 transferred to strong spirit. Teeth may be treated 

 in the same manner. 



In all cases a weak solution should be employed 

 at first and strengthened each time it is changed. 

 The specimens should be examined from time to 

 time, and removed when they shall have acquired 

 the proper condition. The greatest care must be 

 exercised lest they become brittle. When removed 

 from the chromic acid solution they should be soaked 

 in water, frequently changed, for at least twenty-four 

 hours, and then transferred, for keeping, to 95 per 

 cent, alcohol. 



MUSCLE. A piece of muscle from an animal 

 recently killed is steeped in a small quantity of a 

 i per cent, solution for a week. The cleavage of 

 its sarcous substance is shown by teasing a small 

 piece in glycerine. 



NERVE. Harden a piece of metacarpal nerve of a 

 horse, or sciatic nerve of a smaller animal for ten 

 days in a i per cent, solution. Stain a bit in 

 logwood, then tease it in glycerine thoroughly. 

 This shows its connective tissue. 



Chromic Acid and Alcohol. 



Mix one part of a 4 per cent, solution of chromic 

 acid with two parts of methylated spirit. This 

 should be done when required for use. 



The following tissues may be placed in this, then 

 transferred to spirit. The time required must be 

 judged according to directions already given: 



The whole of one cornea, to show stratified 

 epithelium ; a piece of small intestine, to show: non- 



