Dear Yan:
Muscle is  a  tissue  that  deserves  special attention. If you like to cut
it better  I  suggest you to use methyl salycilate as clearant agent,you can
let pieces stand overnight. You can do a last bath in toluene for extracting
some of the salycilate, and then prolong the baths in paraffin doing many
changes, this can take many hours without hardening excessively the pieces.
Good luck, Carlos.Histotechnologist,Montevideo,Uruguay