In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: [ Ca ( 2 + ) ] ( i ) overload induced by aconitine or ouabain was reduced in isolated myocytes pretreated with pilocarpine .
### Output Text:
[ <span class="chemical">Ca</span> ( 2 + ) ] ( i ) overload induced by <span class="chemical">aconitine</span> or <span class="chemical">ouabain</span> was reduced in isolated myocytes pretreated with <span class="chemical">pilocarpine</span> . 